unfortunately you're plagued with some spyware, as 3/4 of the world probably is. My guess is that it's not easy to get rid of. if you're able to, go to http://www.download.com
and go to their spyware section and download a program from there such as AdAware, SpySweeper, etc.. that should fix your homepage error and the poop issue. lol
If you have the recovery disks from your son's computer, those would work too.. Even better. i'm guessing that they have everything copied onto them, Windows, etc.. but i have no idea how to use them. just pop them in and see what happens.
Welcome to the world of technology