Please HELP! Cannot open any Microsoft Office software!

I use Windows Vista. Basically what happens is everytime I open a program the Windows Installer pops up. When I open IE it will pop up, blink off an on like 15 times, then IE will work fine. It also does this when I open a new tab in the browser. The biggest problem is when I go to open up Windows 2003 (I cannot use 2007 as I do not have the product key), Windows Installer pops up and says it is preparing to install. It will take about 2 minutes and finally it will say that it cannot open the program. I get an error message that reads:This update package could not be opened. verify that the update package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer update package.

This is very frustrating. I cannot even unistall Office. When I tried, it said I was missing a patch. I hope someone can help me. I am a college student and need access to Word!

Firstly i would try installing the new 'windows installer' version available at Microsofts website (Windows Installer 3.1 v2 (3.1.4000.2435)
http://support.microsoft.com/kb/893803

Another option you could try is to stop the "windows installer"service from the services.msc (command prompt>services.msc) and whenever u want to install any software u can start the service again.

Once the windows installer service is updated or stopped and the issue with opening MS office still occurs then the problem most likely lies elswhere such as a corrupt program or possibly a malware related issue.

If your still having no luck, or you are unsure, post a current HiJackThis log in the Malware Removal forum and get the experts to take a look at whats running on your system.

Regards