This is typical of infections that can disable your installed antivirus. Try Housecall at
Lately, windows installer has been running by itself at random times. It just pops up and a progress bar begins to fill up. If I click cancel, it re-appears, and this goes on for about 2 or 3 "cancel's" when it finally stays close. For an example of when this happens, it just happened when I launched Norton Antivirus. It has never done this before, and I have not modified Norton at all. Once I get the installer window closed, norton works fine. It has also happened when running a Microsoft office app, as well as a few other programs. Any ideas to fix this would be huge help. Thanks!