windows installer/uninstaller

[Trina]

I have been trying to uninstall my current virus
protection program, and install a new one. But when I try
to do either, I get the following message in a window.

the windows installer service could not be accessed. this
can occur if you are running in safe mode, or if the
windows installer is not correctly installed. contact your
support personnel for assistance
What is it that I'm needing to do now? I'm not in safe
mode, and I've rebooted the pc, did a disk cleanup and
still no luck in getting the windows installer to work for
me. Any help would be much appreciated,,thanks
..