I ended up doing a lot of this on Christmas, because I had just backed up my files to my external hard drive on Christmas Eve, and I figured I would not be using the laptop all day.

Decluttering and organizing my files recovered about 1 1/2-2G of memory, and I also uninstalled a number of programs, such as Open Office, which is never as accessible as I want it to be, and most notably I uninstalled the Google desktop, which had been perceptibly slowing down my computer.

I then followed the tips in this article
5 ways to speed up your PC
http://www.microsoft.com/atwork/maintenance/speed.aspx
( details and links below cut )