Have probably done something really daft but need help (sorry if this gets long)

Had a nearly working version of Zen Cart but did something and it no longer worked, so have tried to reinstall it

I moved the original version of Zen Cart in hope I could copy over my files

But the reinstall was in the wrong place, so I uninstalled and reinstalled, this time, I couldnt find where it had installed (thought it was the root directory but cant see it) so tried to unstall it which didn't work properly

So now I have one partially uninstalled version and another version which is corupted and back in its original place

When I now go to reinstall it, it says I already have a version, but under current installed versions it says none

SO

How do I complete uninstall all versions on my server?

Im using Control panel and Fantasico (and am a relative newbie to all this so please talk down to me)