Torn, it isn't 64 bit dual processors... the recommended business setup is a P4 HT (hyper thread) processor, which is much more than a year old already... and that is the recommended level. That means that there will likely be reasonable performance down to P4 2.4 or so.
http://www.intel.com/business/bss/pr...ns/desktop.htm
it isn't much different from when we went from Windows 3.1 / 3.11 to XP. The cutoff at that point was about 400mhz, which at the time put a ton of PCs into the junk pile.
Alex