Thanks for your reply. I tried that (even though in my windows system the paths seem to be \ ). Anyway, and this is the weird part, I got exactly the same error messsage (with the same path that it told me it couldn' find the first time). It seems that no matter what I put as the path in main.inc.php, the program tries to look somewhere else (that I don't know where and when I set).
I am sure this is a stupid error that I must have made (there is no logic in this...)