Harm Millaard, the hardware guru from the PrPro forum, has done several articles on new systems for NLE work.
Follow the links in these to his postings:
He covers a lot of ground and you will likely get some great tips. Now, his hardware article was done about a year ago, so some recs. might need to be updated a bit. Still, the theories are very sound and mirror my experiences very closely.
While there are a number of advantages to going with the 64-bit operating system, you may run into problems with Premiere Elements 8 on 64-bit Windows 7.
It's not the operating system itself, but the 64-bit drivers the program has to interface with.
It's not guaranteed to be a problem, but some people are experiencing problems with that platform and this program. On the other hand, 32-bit Windows 7 seems to run Premiere Elements 8 very well!