check your system for viruses and malware then post your hijackthis log here

I've never seen this before, have you tried msconfig, to see what starts up on your computer, and see if there are any instances of Windows Installer Present, if so, then uncheck them, and if not, then I don't really know, if they are there, but they keep getting rechecked and keep starting up on your system, you should go to www.download.com, search in the search box for Startup Control Panel, the results it should find, the top one should be Startup Control Panel 2.8, and then install it, then go to the control panel, if you are in category view, go to the left column of the window and click Other Control Panel options, and you should see a link that says Startup, go into that, and look for the tab RUN, on the top, it should have all the startup items that would show in your msconfig area, and then right click on the instances of the Windows Installer Files, and then press delete, and it should be fine, reply to this if you're still having trouble.