Windows Vista eats RAM for breakfast. If your notebook has only 1GB, check out Buy.com's deal on 2GB of Crucial PC2-5300 667MHz memory: $24.99 shipped after a $20 mail-in rebate.
This sale consists of a pair of 1GB modules, so you'll probably have to remove your notebook's existing RAM to make room. (Needless to say, you should then head straight to eBay and unload them). Check the manual to make sure the system supports this memory speed and configuration. It's pretty standard, though, so you should be fine. The rebate deal expires Feb. 24.