Error NwSapFeilg.dll missing when starting GUI 7.20 setup

Hi,

After removing GUI 7.30 from my laptop I've rebooted before starting the setup of GUI 7.20.

Immediately after starting SetupAll.exe I get a 'NwSAPsetup.exe - System Error; The program can't start because NwSapFeilg.dll is missing from your computer. Try reinstalling the program to fix this problem.'.

Does anybody know what I need to do to resolve this issue?

Thanks in advance!