Ah, sorry forgot to tell that I finally solved the problem by throwing money at it.
I already brought it to the shop but it performed well on their test PC but crapped up at home again. I figured out that it has to be the Ide controller so my choices were either a new ide controller or an external case, since I already have no room for more hdds in my midi tower another ide controller would be a waste and for about the same money I got myself a nice and shiny external case for Usb2 and firewire since all my USB2 prots don't like external storage, like in periodically dis and reconnecting.
Now the 200 gig works like a charm, as fast as it would have in the tower itself, at least it feels like that. Only used for mass storage anyway since I still got my raid for games and work and another 40 for system and programs. Now I got 400 GB of storage space, I would have never imagined or have aimed for that much :D.