Hi Load,
Lets work on the first error "***ERROR***: Shortcut entry with name >ShortCut to CA4< already exists in the properties map". Make backup of the sapshortcut.ini. Please edit sapshortcut.ini located under C:\Users\xxxxxxxx\AppData\Roaming and remove the existing entry ShortCut to CA4. Check security of all files under Roaming have the proper authorization's (Read Write etc...) Especially the ones you are having issues with.
If you still are getting and error and must stay on SAP GUI for Windows 7.20 I would update SAPSeup. You can find it at "https://www.service.sap.com/swdc -> Support Packages and Patches -> A - Z Index -> "S" -> SL Toolset -> SL Toolset 1.0 -> Entry By Components -> SAPSetup" It is downward compatible. Reference SAP Note 1583967. If you continue receiving error's run the SAP GUI Installation Check and resolve any issues there.
Make sure right click on the file saplgpad.exe and run as Administrator.
Cheers
Dan Mead