All I can say is, when it tells you only one instance of set-up can be running at any one time, it means you have set-up still running somewhere, and it's probably running in the background

 

For this message to appear, it sounds like you've tried to run set-up again while it's still running

 

If set-up is running, it won't allow you to remove it from your computer

 

Have you tried switching the computer off, switching back on again, then going to add remove programs after this?

 

Ignore my last message, I see you did message 2 while I was typing it lol

I'm amazed a set-up program would remove important files from Windows, all I can guess is it was replacing the files and hadn't properly finished what it was doing?/ didn't accomplish everything?

 

All sounds like bad programming to me (again) lol