I have a Compaq deskpro w/Windows 2000 Professional os (service pk4). I don't have any installation Cd's or access to the network that supported it. My problem is that somehow the Window's installer (version 3.1) has become corrupt. Tried various remedies like MS update, and registry cleaners. But it still will not install software programs completely. Example: Windows media ver 9, I downloaded ok and began installing. It was copying files, updating registry entries, etc, then near the end msg displayed: Installation not complete try installing again. Any ideas?

Try the installer cleanup utility:
http://support.microsoft.com/kb/290301

Ok, I'll give that a shot. Previously I encounteted this err msg:

Local machine: installation failed
Installation:
Error: Action failed for registry key HKLM\SOFTWARE\Classes\AvgDiagFile\DefaultIcon: creating registry key....
Access is denied. (5)

That's a permissions problem.
Are you logged on as administrator?

Yes logged on as administrator. Entire C drive has full rights to everything, which may the cause of problem becuse I think a trojan has infected it.

Reg editor won't let me change that data value. Don't want to buy RegCure for $30 just yet

Trying everything, reg cleaners, etc. Apparently I am missing a file called "msiexec". Can't download it from Microsoft update. Can't find it anywhere using search engines (google, etc).

Can anyone email it to me? Thanks, Flofox

Problem solved. Thanx to all who gave advice. I had my daughter email me (attch) "msiexec" which is the heart of Windows installer. I put in the system folder where it belongs. Then I had to reregister it internally so my machine would use it. And it worked. MY AVG trial had expired when I reinstalled AVG it found some trojans.