Depends largely on your processor. My desktop is a quad processor and can run either but is supposed to have better performance on 64. My laptops are just running 32
Basically a 32bit can only handle 3.2 Gb or ram ,64 bit can handle 12 Gb
When i was getting my current rig built ,many of the places i asked at ,attempted to sell me 4Gb of ram ,effectively trying to rip me off for the cost of that extra 1Gb.
thats all i understand about it .how many Gb of ram do i need for my gaming
Actually 4Gb is the limit for a 32-Bit Processor, it's Windoze that can't access much above 3.2 or 3.5Gb (this seems to depend on the OS, my PC at work shows 3.5Gb in Vista Business but I've seen 3.2Gb reported on other machines.) You need a 64-Bit OS to take advantage of any extra RAM that a 64-Bit processor can handle, but unless you are really hammering the PC I would suspect that 4Gb capped at 3.2 or 3.5 or whatever your OS decides it can cope with would be adequate.
The above article suggests that the maximum RAM for an AMD 64-Bit chip is 256 Petabytes or 256*1024=262,144 Gb of RAM! Good luck finding a motherboard with enough DIMM slots for that though
If you're only a light PC user I wouldn't worry about the two different OS's, no need to complicate matters.
Vista, after service pack 1 update can address 4 GB's of RAM, although I'm not sure if it uses it all.
I'm using 4 GB's of RAM in Windows 7 Beta 32 bit, and for my needs it works perfectly. Main use is gaming, photoshop and some video encoding, and it's perfect for my needs.
Are you looking to buy/build a new PC? If so let us know and we can help you out