Hi M,
One of many reasons this can happen:
1-- The CD is damaged for the software or the installer corrupt which came
with the software?.
2-- The Windows Installer is damaged and the installation not success or
complete?.
Try to clear your caches and delete all the Temp by running the Disk Cleanup
( note make sure your system is not Password Auto complete or set to remember
the password, or you will lose your saved Passwords on your Disk if you run
unselective Cleanup procedure?).