Suggestion to try:
Unregister, and then re-register Windows Installer. This procedure corrects most
situations, and does not affect any currently-installed program that uses the
Windows Installer.
To unregister and re-register Windows Installer:
Click Start, and then click Run.
Type in the Open box: msiexec /unregister and then click OK.
Click Start, and then click Run.
Type in the Open box: msiexec /regserver click OK.
Type commands exactly, including the space between c and /.
This will not affect programs which use Windows Installer that are already
installed.