FYI. I had previously gone from 2-512mb sticks to 2-512 and 2-1gb of RAM. Huge improvement in my Vista PC. Crucial.com has a sale going on and just ordered 2 more stick of 1gb RAM last night. Cost was $34 +$3 shipping. (Will have 4-1gb once installed)

If you need more ram, may want to take a look now. Seem to have had a price drop and much more affordable.

(I mentioned Crucial because I have a corporate account there, may want to take a look at your vendor of choice)