My in-game runs at least twice the speed and won't slow down, this makes combat really tedious i think i got at least 500 fps or something in that game...
it's insane...
Anyways to slow down the game?

Unreal also runs 3 times the speed on my computer, but that's for another time...
How can i slow down this game?

I'm on a Windows XP

Try turning on VSync to limit your FPS.

Vsync is on, and graphics are at max, even gave OpenGL a try, no reduction...

The game runs like a "general speed" hack is active... no stuttering or anything, substitles are running fast too...
I'm at a lost - for once - as to what to do ... NEVER encountered a game to run thus fast - sure i tried with slow, but not fast...

Hope someone have a solution...

Try this: http://www.cpukiller.com/
It's like putting heavy stones on you just to make yourself walk instead of running.

I'm not sure if this is a solution, but try alt+tabbing out of the game and setting Core Affinity to 1 in the task manager. That sometimes fixes problems like this.