RAM upgrade.

Running Vista home premium on 1gb of memory was an exercise of patience I got tired of. An upgrade to 4gb made a big difference. 4Gb for under $100 was too good to pass by. RAM upgrades are bar none the best thing you can do for any system hands down, and should be the first step in any system upgrade.

Opening or closing any application is like flipping a switch. There's virtually no wait. I've noticed spyware/virus scans go quicker too. The install took all of 5 minutes and my pc recognized the upgrade immediately with no problems.