I'm not saying 64 bit OS isn't better than a 32 bit OS. But I am still using Windows Vista 32 bit w/6g of RAM and am able to multibox just fine.

Might investigate your cache settings. There's a lot of things you can do to improve performance tremendously for free. Basically increasing your HD cache size should help a ton and it's free. Here's a guide I found on Techspot:

http://www.techspot.com/guides/72-wi...mory-tweaking/

What you're really interested in is page 5 of the article:
http://www.techspot.com/guides/72-wi...ing/page5.html

If the tweaks don't help then not much else you can do but upgrade I suppose.