As true as it was several years ago it stands today, the cheapest way to increase a system’s speed is to increase the amount of ram up to a certain amount. The magic amount used to be 4GB and it seems to be increasing to around 8-16GB especially with Microsoft pushing 64bit. Fortunately Crucial has put out a 8GB sport kit with surprising results.
Slow computer got you down? Maybe a hardware upgrade should be in your cards, if so this guide to the Fundamentals of Upgrading a PC is an invaluable read. PCSTATS Tips