Fix Windows Installer "Invalid Drive" error

Problem
You may get an error like this when trying to install something on Windows (Windows 7 in my case).

You may assume it is caused by an inaccessible network drive (e.g. H in my case) and that disconnecting the drive will solve the problem. It didn't for me.

Rebooting also didn't solve the problem.

Then I found this Microsoft article, which was rubbish.

Then finally I found this Microsoft Technet article and the top answer over there solved my problem.

Solution
The Technet article recommends checking the following 2 registry locations:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders
and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders

In the first location I found this. Note how there is one reference to drive H, the rest are to a system var %USERPROFILE%.

Simply modifying the path H:\Favorites to %USERPROFILE%\Favorites solved the problem immediately. The installer ran perfectly without throwing up the "Invalid Drive" error.