I have an old Athlon 3200+ 2.2 GHz machine, running fine for past five years, very very soon to be sixth (tomorrow is its birthday, lol). It's got 1 GB of DDR RAM and a GeForce 6800. I want to install W 7 on it, but I can only find a 64-bit disc. I know MS says that the requirements are 2 GB for 64-bit, but I've heard of others managing to install 64-bit fine on 1 GB RAM machines. I'm only going to play a few FPS games with low requirements.
I know 32-bit would most likely run faster than 64-bit, but I just want to know will 64-bit run OK without too many problems, and will ReadyBoost help with this? I have several USB flash drives that would seem to qualify.
I recommend against it as well. Windows 7 is designed to run off 2GB of RAM. Anything less than 2GB will result in significant slow down, as the OS itself takes up around 400-500MB depending on what settings you've configured. Applications like FPS can easily run up the 500MB mark. This will bring you dangerously close to 1GB, and your computer will begin to use virtual memory which will bring you down to crawling speeds... I wouldn't even recommend running 32-bit with anything less than 2GB. Especially if you're looking to play a few games. RAM is an inexpensive way to upgrade your computer. Do it.
Get more RAM.
Stick with XP.
Or prepare for pain.
Or find a 32-bit disc.
Windows tends to low ball the recommended/necessary hardware for an OS which is what gave Vista so much hate. HP and Dell sold most of their computers at bare minimum specs, you'll hate windows 7 if you try to put it on there, it may run stable until you start launching programs but I wouldn't suggest it. If this computer is a toy you play with only for web browsing and playing movies/music it may work but be prepared for some possible pain.
This is one of the few situations where ready boost may help you as well.
I installed 32-bit Windows 7 on a machine with only 768MB of memory. It installed and worked just fine, although I never tried to run anything heavy on it and I basically just used one application at a time.
I'm pretty sure you'll be able to install and use 64-bit Windows 7, but I'd consider it a "lets see how this works" system and I wouldn't expect to be able to run anything substantial on it.
Anyways, I got to play with the system and it ran surprisingly well. I didn't pay attention to RAM usage or do anything really stressful like run a 3D game, but it ran pretty good. Not as snappy as XP, but not bad at all.