Windows XP x64 comes in 2 variants.
Windows XP x64 and Windows XP x64 Professional Edition
The professional edition is Windows 5.2. Some programs do NOT like it, I think it's the way some programs identify them, if it's not 5.1 but above, then it may refuse to install. Doom 3 needs to be modified to be installed, once it is, it works perfectly. Some games do not like the "Windows XP" compatibility mode, but work better when it's left standard.
Windows XP works well with 1GB RAM, but an ideal minimum is 256MB, many places say 1GB but that's for games, etc
Windows XP x64 Pro needs 256MB RAM it would be better if applications worked better. Some of my game work better on XP 32 but crash completely on XP 64.
Windows Vista 32 I haven't played with too much, it doesn't seem much of a problem with 2GB RAM from what I remember. I always use 64 bit OS.
Windows Vista x64 seems ok on 2GB RAM. I run it on 6GB RAM and ran Daemon Tools lite and was wondering why I had 14% free memory. One of the mounted images was completely mounted in RAM, not bad for performance I suppose. But not many applications are optimised for 64bit.
You can get 64bit patches, but they aren't proper. There are drivers fr graphics cards that are said to be better than 32 bit. This could be the way they are executed and stored in memory before going to VRAM. I wonder how long before Windows will become 64 bit only. The leap from 16 to 32 bit wasn't as long as this. Windows 3.x and Windows 95, although Windows 95 emulated 32bit, and Windows NT was the true 32bit OS in the family. Why do you think Windows 2000/XP was MUCH better in speed?
Windows 7 could be the next stage where it's 64 bit only, who knows. I know that Windows 6.1 is in beta for 32 and 64bit, so why is Vista much better on 64 bit platforms?
Is it so hard to want a 64bit operating system that needs little to run, run my games natively, and not be rubbish? I know Linux is out there, but I want all my games to run. Windows Vista x64 Ultimate 6.0.6001 wasn't too good at running Unreal Tournament, it had a speed problem, whereas Unreal Tournament on Windows x64 Pro ran better (I have dual cores, all drivers necessary were installed) and smoother. Windows 5.2 and above will not run DOS based games such as Blood, Duke Nukem 3D, Shadow Warrior and other DOS based games without something else to run it on between the OS and application.
Linux has good compatibility. Quake 3 Arena installed under Windows, runs well through Wine. I just need to get to know the commands for it to hopefully tweak it to it's best for me.
I love the way computers are getting faster and operating systems need more to run as time goes on. So the end result is; boot time is the same for all computers regardless of what it is running. Unless you have a severe problem and Windows Vista takes about 45 minutes to load... I'm not joking... A quick chkdsk with chkntfs adjustment (I am told chkntfs and chkdsk are the same? lol, whatever) and it was improved dramatically