Windows Installer keeps activating

I have windows xp home os. I caught a virus or something. A couple weeks ago it started. Most of the time when I start various applications windows installer activates asking for installation path while the program starts fine. No perticular program does it. Also a lot of times installer activates on right click. The only way I can almost stop it is disable windows installer services. Then it still pops up a lot of times for a second and then disapears. Can ya help me on this, I can’t seem to figure it out on my own. Thanks