Ok so 64 bit is needed to utilize all my 4gbs. BUT I do not want to have any problems from the OS not being compatible.

Straight answer, which OS is best?

Vista 32
XP 32
Vista x64
XP x64

??

I have no problems with XP32; I see 3.2GB of my 4GB. Whether or not the others might work, they aren't necessary (and I know Vista is not compatible with some of my programs).

I think I've seen more people complain about XP x64 lately than people complaining about Vista x64., so I would narrow down your choices to XP 32 or Vista x64.

I have run Vista x64 for over 2 months now and never faced any compatibility issues, but all my parts are 2 months old as well. I had partitioned my disk to be able to install XP 32 as well, but never needed to. Some people love Vista, some people hate it and some people just don't mind (like me).

Are you going to add more RAM later? If the answer is yes, x64, if not, 32 bit will get you by.

I would go with vista 64, some of the security features can be annoying but overall I like it. I have had it for around 7 months now and have run into very few compatibility issues, if at all. It isn't a terrible OS like some people say it is...

I'd have to recommend Vista 64. I'm sorry, but don't believe the nay-sayers, Vista's there with the 64-bit version. Its fast, its fun, its stable, it works, and it looks like a contemporary OS. Wanna see it really fly? Feed it 8GB of RAM when you have the opportunity.

I have vista and xp 64 bit versions, I prefer Vista for most stuff, but sometimes they're trade offs between the two. Like I get lower performance in Vista when I play Quake Wars, but I get glitches in XP after I play a campaign.

BTW, only program that wouldn't work for me in either O/S is zonealarm because there is no 64bit client available (at least there wasn't when I first got xp 64 and I haven't looked since).

XPx64 will use all the ram and be the fastest over all. Compatability
problems still exist but drivers are not the problem they were a year ago.
Second in line XP 32bit.
Third tie. With only 4gb of RAM I don't see any advantage 64bit or 32bit VISTA.

OH Sorry...Straight answer. XP 32bit

Opinions are like Butts. Everybody has one.

If you want to see your 4 gig obviously you need 64 bit. If you go 64 bit, Vista has the advantage in that all WHQL drivers for Vista as I understand require a 64 bit version. This was Microsoft's way of pushing the industry to finally transition to 64 bit. Someone else can elaborate or correct me but I seem to recall this being one big difference with Vista.

I just built my "HTPC" PC on Sunday night and this is my first 64 bit PC. My reasoning was that I want an HTPC to be responsive and what better way to achieve that than feed it ram (8gig). So far in my limited experience I've had no problems with being on Vista 64. I had to do a little digging to find a driver for the linksys wireless card but otherwise 64 bit has not been a problem.

Thanks for all the replies. Im still uncertain though. I wish microsoft would properly support 4gbs+ of ram but oh well gotta chose.

What about partioning my drive into three and installing Win XP 32 on one partion, vista 64 on the 2nd partion, and use the last for .. well i guess media since programs will have to be installed twice I assume.. once for xp and once for vista..

With 8GB Vista 64 has just been rock solid, IME. A few months ago THG put out an article on 8GB of RAM for Vista, disabling the page file, and so on. I turned off my page file and haven't looked back since. For me, Vista64, 8GB, no-page-file just plain flies. I fire up VMWare WKS with 2-3 clients running simultaneously and they work like I'm used to machines working on physical boxes. There's no stops, no hesitations, no questions, its just fast. In fact, just for nostalgia sake I installed, cough, NT4.0 WKS, in a virtual environment and was blown away by the performance...while a Vista32 and XP32bit client were simultaneously running on the Vista64 host.

Vista 64 is finally really getting there. I've had no driver issues to speak of in the past 9 months. Yes, XP64 may be faster, ...and I'd imagine that Win2K would be even faster yet, DOS would be faster still.

With the price of DDR2 as low as it is I'd say spend the ~$160 (if you can) and go for 8GB and enjoy Vista 64's features, interface, and stability.

I imagine that many enthusiasts, myself included, dual-boot XP32. I like the security of knowing its there in the event there's that ever-so-rare compatibility issue. ...but I rarely need it ...or use it. I hear that gaming is much, much, much, much better on XP so you may want to keep it for that, but truth be told its been rarely-used hard drive space since I got Vista 64.

I've been using Vista x64 and I haven't had an issue yet in terms of compatibility. in fact other than having to hunt down direction on how to turn off the user account control I really cant say I've had any major issues at all. personally, I think its significantly ahead of XP, and I really dont understand why people keep bashing it. the one biggest complaint that I hear is that its a memory hog, but if we look at the history of the windows OS's memory requirements:
1995 win95: 4MB
1998 win98:16MB
2000 winME:32MB
2001 winXP:64MB(128MB reccommended)
2007 Vista:512MB(1GB reccommended)

from 95 to 98 we had a 3 year gap and the RAM requirement increases by 4x or 1.33xper year
from 98 to ME we had a 2 year gap and the RAM requirement increases by 2x or 1x per year
from ME to XP we had a 1 year gap and the RAM requirement increases by 2x or 2x per year
from XP to Vista we had a 6 year gap and the RAM requirement increases by 8x or 1.33x per year

looking at the trends of the past OS's vista falls right in line with what you should be expecting in terms of the RAM usage.

Another vote for Vista 64 bit. See sig for explanation.