Like Saab and GG, I'm baffled. You're building a new computer, to 2010 spec, and then installing Vista on it? Why on earth would you do that?
If you're giving the old PC away, with the Vista that's on it, then you can't use that Vista on the new one anyway.
If you're installing 4GB of RAM, either you're going to waste some of that, or you need the 64 bit version of Win 7. As they say, make sure there are 64-bit drivers for all the peripherals you want to use.