If you are buying new they most likely will, its just older or less popular pieces of hardware don't always have a working 64-bit driver. The list of incompatible hardware isn't that big these days and MS have good generic drivers for allot of older hardware that work quite well. You should always check if its Vista compatible before you buy but they do stick the Vista compatible logo on almost all new electronics hardware these days to make it easy.
OK thats good to know, thanks.