Can't Find File msiexec

I'm trying to work on an update problem. I have a HP trouble shooting
procedure that calls for unregistering and reregistering file msiexec.
When I go to Start>Run>msiexec I receive a message stating that
msiexec could not be found. I find the file at
C>Windows>system32>msiexec.exe.and in the registry at
Windows>system32>msiexec.exe. Any help would be appreciated. I've been
fighting this download problem for months. I can download updates, but
can't install them. Thanks