Ok so I am convinced to install Win7 Professional on a separate HD. Now my problem is choosing between the 32-bit and 64-bit versions. I have read some basic differences between them, mostly the RAM memory capacity difference and more security features. I have also read about device drivers required to be digitally signed and that certain software not supporting 64-bit.
What can I expect? Are there categories of software that don't support 64-bit? I mostly game and go online, with a little video and audio editing thrown in there.
 
Overall, whats the verdict?

Not getting 64-bit is like installing Windows XP. It is the future. I haven't had a single problem since I started using Vista 64 in 2007. 

While I'm not highly knowledgeable about the differences and subtleties of Windows 7 32-bit versus 64-bit, I do know that I've had no big problems while running 64-bit for awhile now.   Every now and then I'll run across an application that doesn't support 64-bit, but usually I've been lucky enough to find a beta version that works. I've also used a lot of 32-bit programs that seem to work fine. I haven't had any problems with game installs, although this laptop lacks a DVD drive so it's strictly Steam for me.  
 
I'm probably not much help, but thought I'd give you a generalization of what I've been experiencing, because originally I was speculative too.

64-bit is the future, apps that don't support it are usually aged websites and aged games. You really wont find that much that doesn't support it, this isn't the dark ages where every developer was scared of Vista. 
 
Get the 64-bit. And get rid of the POS Windows XP if your still using it...

" @csoup:  I actually am. I want to keep WinXP on one drive and Win7 on a separate drive. "

" 64-bit is the future, apps that don't support it are usually aged websites and aged games. You really wont find that much that doesn't support it, this isn't the dark ages where every developer was scared of Vista.   Get the 64-bit. And get rid of the POS Windows XP if your still using it... "

64bit for more memory. I have win7 around about it has come out and have had 0 32bit issues. All 32bit software plays great.

always get 64 bit 

Go for 64-bit. Especially if you use your computer for more than just dicking around (ie, Adobe software, Maya, Rhinocerous, Autodesk etc) you will be much happier you didn't go for the 32-bit.

" 64-bit is the future, apps that don't support it are usually aged websites and aged games. You really wont find that much that doesn't support it, this isn't the dark ages where every developer was scared of Vista.   "

64 bit is the way to go,  depending on your mobo you can toss a lot of RAM in there. I think my board offers 16gigs max, not sure since I'm at 8gigs and have never thought to myself ''this could be faster''. 
 
Also, you can scrap the XP dual boot idea.  Once you use win7 64 you wouldn't miss anything that XP has to offer, and if you go with win7 pro it has compatibility mode for XP sp3.

I'm with everyone else, 64-bit all the way. The biggest advantage you'll have is that you can access 4GB+ of memory on 64-bit, while you can't on 32-bit windows. There are also some security enhancements, but I doubt those will be of much use to you.

Get 64-bit. Everything works. It runs better. End of story.

Thanks for all the info everyone. I'm convinced in getting Win7 Pro for all the reasons you stated above and that.......I'm still running WinXP. I do have older software but hopefully the backwards compatibility feature on Win7 Pro will be able to handle it.

no real disadvantage to running 64-bit windows, unless you by chance want to run a 16-bit application which 64-bit doesn't support.

When Win 7 came out I had to install the 32-bit version because I had a Dell printer and they never released 64-bit drivers for it. I've since gotten a much better printer and reinstalled the 64-bit version of Windows. My dad's work computer has to run the 32-bit version because he has an industrial laser hooked up to it and there are no 64-bit drivers for it. Other than these two issues, I haven't run into any instances of problems with running 64-bit Win 7. Unless you have a really old or specialty piece of hardware, go 64-bit. If you do have something like that, check for the drivers before installing.

64 bit vista hasn't given me any major issues. 

64 bit might have been a problem in the xp days , but really now , the only reason 32 bit versions of windows still exist is cause there's a lot of processors that dont support 64 bit instructions .  ( mostly laptop/netbooks )
so unless you have one of these ancient processors , go with the 64 bit version.

" @MisterChief:  That might be true. I'm just paranoid with incompatibilities. "

This isn't even a question.  First get rid of XP, microsoft has already publicly said they will no longer support it as an OS.  I mean be real that is about as clear a sign as you will ever get it is time to move on.  As for 64 bit, don't be stupid, 64 bit is not the future it is the current standard.  The next version of windows which is rumored to be around sometime in 2012 will not even have a 32 bit version.  Nuff said.
 
Oh and PS: The high end versions of 7 even have an "XP mode" so they can even run apps that were "XP only" and would not run on vista.  There really is absolutely no reason to be running XP today short of having a crap pc with no ram.

just get 64 bit. there's a download for an xp virtual machine on the microsoft website, so you can just use that if need be.

THE FUTURE! 

Well one of them supports a normal amount of RAM, the other one doesn't, seems simple to me. 
 
HINT: It's the 64 bit one you want. 

I am using 64-bit Windows 7 and no problems for me. I think you should pick the better one and that is obviously 64-bit. 

All the cool kids run 64 bit.  

That is pointless. 

I was weary going to 64bit Windows 7 from 32bit XP and have no regrets. 
 
1) DEP has never broke any of my games and I have run well over 100 retail games on this PC. The closest I've got to DEP interfering with me running something game related was a funky console emulator and I forget which as I found a better emulator without said error. 
 
2) Games running in WOW64 have a negligible framerate hit (think less than one) and are further nullfied when said games are optimized for multithreaded processors. 
 
3) If your CPU can handle 64-bit and have a funky audio driver issue (like I do), you'll still survive using Microsoft's generic driver (as I do). 
 
4) There's a good chance you can run that old-ass problematic game you love so much through virtualization software of your choice. 
 
Don't be held back by whatever anybody else might say to scare you off from moving forward. The industry is moving to 64 bit for a reason and that is because demands of the RAM is increasing and 32bit limitations simply can't cut it anymore.

The only problem I've ever had is when I'm working with Adobe Audition but it still works... The screen just goes all wonky for a moment and the desktop colors look off. I vote install 64 

" just get 64 bit. there's a download for an xp virtual machine on the microsoft website, so you can just use that if need be. "

" hahaha -  aww... all you funny people. 
 
I keep a 32-bit XP and a 32-bit Vista AND a 32-bit Win7 on one machine for g a m i n g. There a not more than probably 10 games which support native 64bit binaries - the rest of all your PC Games are running only in 32-bit.
 

• the 'security' (DEP) you gain with 64-bit Win OS makes older games break or not run without modification.
• if you run your games on a 64-bit OS it is using the Windows-32-on-Windows-64 (WOW64) compatibility layer = it run's in compatibility mode.
• drivers are now ok (to the vendors quite a while - many gaming related issues came from audio device drivers - 64-bit OS cannot run 32-bit dll's) but you still will have some incompatible sound-driver issues due to old games & API calls.
  
• some older games depend on old DirectX versions and even old OS handling (example: Metal Gear Solid 2 for PC runs in XP - not in Vista/W7 AFAIK)

 
... so, while you're good, if you run mainstream software on your Windows 64-bit PC - PC Games especially do not profit from 64-bit unless they are patched or optimized (using the additional RAM, running 64-bit binaries).   I hope, this helps to see things more clearly, beyond the random: "64-bit is the way to go/future" blah. :) "

• While it's true that very few games have 64-bit executables, having the OS being able to address more then 4GB of RAM without kludges (such as PAE - which is shit and slows performance in some cases and can be extremely finicky to get running correctly with certain CPUs and Motherboards) can mean a world of system performance improvement overall, which in turn means your games should and often will run more smoothly (less hard disk access and quicker level loads).
• DEP is common to all MS Windows since XP Service Pack 1 and in Vista AND 7 DEP runs independently for 32-bit and 64-bit executables.  Neither interferes with the other. 
  
• WOW64 has no performance loss and it does not run in compatibility mode.  It runs in its own 32bit HAL.  Lern2WindowsNT.
• Drivers for 64bit OSes haven't been an issue for a long time.  The sound driver issues aren't to do with 64-bit but rather Windows Foundation vs DirectSound3D/MME and have been a problem for some really old games since Vista 32-bit.
  
• Some extremely old games may have some issues running in any modern Windows OS, regardless of bit-width, especially those using really old tech like WinG or DirectX5 - this has more to do with those games using outmoded technlques rather than the OS being the problem.  There are many older Windows 3.11 games which don't run properly or at all on XP.  Oh and Metal Gear Solid 2 can be set to run fine in Windows Vista and Windows 7 - 32 and 64-bit editions.
  

I have used windows vista and windows 7 64-bit versions. i never had any problems. go for 64!

" @SeriouslyNow:  true - DEP is no pro/con 64-argument. My bad. I stand corrected.
 
---
 
I'm not really into forum-thread fights, so I limit myself to one last post in this one: Performance and Memory Consumption Under WOW64 
 ... according to Microsoft's very own Microsoft Developer Network - date: 1/27/2011
 
The bigger point I was trying to make earlier is that after some years now, developers are still writing 16-bit software for 32-bit systems (analogy!). The support-related complaints on publisher forum sites too many times still have a "64-bit" in the title. 32-bit games on 32-bit OS (if you have it) cannot be a bad idea? There are still games out there, which cannot handle more than 2 GB RAM, etc etc... "

Processor hardware. Instruction emulation is performed on the chip. On the x64 processor, instructions are executed natively by the micro-architecture. Therefore, execution speed under WOW64 on x64 is similar to its speed under 32-bit Windows. On the Intel Itanium processor, more software is involved in the emulation, and performance suffers as a result. 

There really are no disadvantages to getting the 64-bit version.

1. Games, we're talking about GAMES.  Games do not run out of threads on ANY version of Windows from XP onwards, regardless of bitwidth.  This discussion has always been about games.  If you are running something which creates lots of threads such as a high end 3D Renderer or Mathematics application chances are it has a 64-bit version and that's all that warning of potential performance decrease pertains to - Run the Appropriate App in the Appropriate Kernel Space.  Also don't be specious, you don't want to learn anything.  What you want is to find the limit of my knowledge and 'beat' me.
2. It's called THUNKING and all that means is that 32-bit instructions and memory addresses are translated into their 64-bit equivalents with respect to the kernel and HAL's respective locations in RAM.  The Windows NT kernel and the architecture we run on these days does almost all of that in faster than realtime speeds (hence the nature of branch prediction technologies being so prevalent in x86 CPU architecture over the last decade and a half).  It's nice that you understand some of the remedial principles taught in high school computing classes.  As you say some 32bit apps can run even faster on a 64-bit OS and this is because the 64 elements of OS can exploit the 64 elements of the base architecture faster.  Adding another layer doesn't always equate to slowdowns due to complexity.  In a system which already complex, another layer may mean more options for dynamism when it comes to things like data access and memory allocation and this is exactly what happens to make some 32bit apps run faster on a 64bit OS than they do in their native 32bit OSes - shortcuts can be taken which can lead to better performance because the host OS is only offering whatever resources are necessary to run said 32bit apps dynamically rather than having to have them always available in the case of the 32bit OS.
   
3. Offtopic PAE vs x86_64 comparison - different kernel, different OS, different demands and entirely unrelated to this discussion. 
   

Reading this thread has made me regret somewhat my original decision to install 32-bit Windows 7 on my laptop w/ 4 GB of RAM.

Why would you want to use 32-bit Windows? This is 2011 people.

" Ok so I am convinced to install Win7 Professional on a separate HD. Now my problem is choosing between the 32-bit and 64-bit versions. I have read some basic differences between them, mostly the RAM memory capacity difference and more security features. I have also read about device drivers required to be digitally signed and that certain software not supporting 64-bit. What can I expect? Are there categories of software that don't support 64-bit? I mostly game and go online, with a little video and audio editing thrown in there. Overall, whats the verdict? "

Having used both, I can say that 64 seems more stable, and I haven't had any compatibility issues with x86 programs.

I'm using 64-bit Windows 7 and it's working great for me. Haven't run into too many problems and it gives you the option of adding more ram if need be. 

" Why xp is better than any other OS.  "