Cannot install Windows Installer 3.1

Trying to run Dell's Support Center I received a message that the Windows Installer Service could not be accessed. It continued stating that the Windows Installer is not correctly installed.  I went to Windows Installer 3.1 web site and downloaded and saved the file to desktop.  When I ran the program I received another error message stating that Setup has detected that the Service Pack version of this system is newer than the update you are applying. So I can't reinstall Windows Installer 3.1.  What am I to do to correct this problem?  Help!  I might add that there are other updates that cannot be installed due to this problem.