As ever so often, one last idea comes after posting your problem...
The solution was to open up a command shell by using admin rights: right-click on the target, select "Run as Admininstrator..." (shield icon) and enter "service.bat install" from there. Note you might have to reopen/refresh your Task Manager or Service Window.
Thank you. I can't beleive I missed that as I have had to deal with "run as admin" with other things yesterday.