Alright, tried the latest Knoppix, still crashing. Tried an alternate linux partition manager, the name of which I don't remember, which also encountered errors. (very inspecific ones)

Finally just decided to install it (Kubuntu) to my secondary hard drive. The partition manager in the installer, which is apparently based on QTparted as well, also refused to do what it was designed to do.

This topic is probably no longer directly related to Knoppix, so I think I'll call it a day and stick with Windows XP for a few more months. Maybe the new Ubuntu version will do better.

Thanks for the suggestion!