Ok I've installed XOOPS in a 'test' directory - can I ask - is there an 'easy' way to move the whole installation - so it's currently in www.website.com/xoopstest and I want to move it to the root - is there a quick way of doing this - is it possible to simply copy the directories?

Or would it be ok to just set up a redirect from my website root to that directory? Or if I eventually have lots of visitors will that coause unnecessary slowdown...?

You could set up a redirect, a lot of people work like that so that the root doesn't get to clutered with directories. If you want to move it, just copy all the files to root and then open up mainfile.php and remove 'xoopstest' from the physical path

I asked pretty much the same question in the Beginner's forum. You may want to take a look in there, but the gist of it was:

Move it, then make the necessary changes in mainfile.php.

I haven't looked in mainfile.php yet, but apparently it's commented enough that finding the proper things to change is doable.