Skype/MSN does not install

Skype/MSN-upgrade got stuck and did not want to install.

It was launched by MSN and everytime it halted with a message like this:
A previous installation was never complete

The solution was to do this:

1. Run regedit (Start->Run->type regedit, press enter).
2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager
3. Double click on PendingFileRenameOperations, copy the text and then remove it, press OK.
4. Run the string you copied (Start->Run->paste string, press enter), make sure it only contains the path to the Skype installer.