^^^ you can also get a large performance boost from a new hard drive.
most hard drives that ship in laptops have a 2mb cache. this is relatively small, and i notice a difference between hard drives that have a 2mb cache vs an 8mb cache.
i recently got a new hdd from ebay with an 8mb cache. instant difference. it was a samsung 60gb unit, same size as my hitachi. the msrp is about $70, got it on ebay for $30, including shipping.