My XP machine, with the Athlon 2.3 gHz processor (single core) has two gig of RAM and runs many tracks and plugins without problems. His processor is faster than mine, but he lacks the RAM.

The key is *available* RAM. Having 1 gig may be fine unless only a small portion is free. I noticed a huge increase in performance when I added the second gig.
Adding a second drive for the incoming audio was the second most noticable improvement here, but that only applies to recording multiple audio tracks.

Make your sound your own!
.. I do not work here, but the benefits are still awesome