SoCal App is absolutely right to recommend a decent graphics card - that makes far more difference to Win 7 than an extra 4 GB RAM (IMHO).
What I have done is to start with 4GB RAM and 64-bit Win 7, leaving half the memory slots free to upgrade (double the RAM) should I feel the need.
I have 2 systems running win 7 - the slightly older PC has the same AMD dual-core CPU (2.4 rather than 3GHz part) and RAM as the newer system, but an AGP 8X video adapter, and is waaaay slower than the PCI-Express system as a result (I eschew the aero interface on the AGP system). Hence comment above!
I haven't encountered too many problems with 64-bit, other than drivers: I've had to work hard to find 64-bit drivers for my printers and scanner - and I've given up on the DAB radio PCI card. To be fair, I think I'd have had problems with win 7 32-bit drivers for those as well, judging from the research I did.
SD