Emmo, mine are still registered for XX5 & XPG&D10.
templop64.dll is not the same as templop.dll.

You must be running the Regsvr32command from the Command Prompt.
I would also Run as administrator.
The Regsvr32 "C:\Program Files\Xara\Webstyle 4\dlls\templop.dll" line must include the double quotes.

Acorn