Error 1327.Invalid Drive: [drive letter]

Error 1327.Invalid Drive: [drive letter] is an error which plagues Adobe and Microsoft updates. It also affects other programs which rely on default windows paths for their installations. Error 1327 is a Windows Installer error which is encountered when the default windows user paths are not available or accessible. There appears to be very little information about how this problem occurs but, it appears to me that the most common reason seems to be related to default user profile directories such as My Documents and My Pictures being moved to non-default locations. Regardless of which software has the issue, the repair remains the same because the issue is related to Windows Installer, not the program that is actual being installed!

This information is confirmed by Flexera Software, the makers of InstallShield here. Due to the fact that Error 1327 is a problem with Windows installer, it will affect all versions of Windows.

Luckily this error has the same fix as Microsoft Error 1606: Could Not Access Network Location which has a Microsoft Fix It wizard to automatically repair all the damaged registry entries. Works for me!

Lets begin by backing up the registry

Choose your Windows version and follow the linked instructions for backing up the registry, this will allow you to revert any changes if needed.

Windows XP: http://support.microsoft.com/kb/322756/

Windows Vista: http://windows.microsoft.com/en-US/windows-vista/Back-up-the-registry

Windows 7: http://windows.microsoft.com/en-us/windows7/Back-up-the-registry

Next download and run the Fix it tool to automatically apply the required registry changes