When an ordinary user tries to install a MSI (Microsoft Installer) package, they receive errors similar to the following:

Error 1913, Could not update the file... Verify that the file exists and that you can access it. 

Error 1321 The Installer has insufficient privileges to modify this file: 

Error 1401 Could not create key: .
The user may receive additional messages, but the error message is generally due to a lack of permissions.

This is usually caused by NOT granting the SYSTEM account Full Control on all files and registry keys.