This is why whenever I buy a computer or a laptop, the first thing that I do is to slick the damn thing and install the operating system as I see fit.
Whether this be Windows or some flavor of *nix, I just wipe out all the partitions and install from fresh.
I learned that lesson with an HP laptop I bought in 2005. No matter what I did, no matter what I uninstalled, I could not get more than 45% of my hard drive free.
I did a fresh load of XP and low and behold, I was only using 10% of the drive with Office, XP, my music files, a couple of games and my applications in my "Must Have" list.
Ever since, I do this on all of the ones at the hospital. I made a fresh load version for every configuration we have and I keep an image saved on our servers. Since we don't allow anything to be saved on the local computers that are on the hospital floors (our way of enforcing HIPPA on our electronically protected health information (EPHI)), this means that if someone sneaks online and lets slip in a virus, I can just wipe-restore from the network, run updates, and the computer is back in business in usually less than an hour. Less than 15 minutes in some cases.
For administration PC's, it's a bit longer. I have to backup their data first and then slick and reload. Then I have to put the data back. So that's more in the 30-90 minutes category.