Less than 1fps?!

[Samuska]

Hey Guys.

Just spent £30 on the game from steam and at the moment, its completely unplayable.
It takes an age to open, the sound is jumpy, mouse is slow, and the game is hopelessly jumpy and between 1 frame every 2-3 seconds to maybe 5 fps.
Ive tried everything I can think of and it still runs like a sack of....

Its not my pc, or at least, i would gladly eat my own feet if it was.
Im running a liquid cooled AMD Phenom II 3.2ghz quad core, 8gb ram, an a HD 6870 over clocked 1gb gpu.
I can run Crysis on ultra with the high res pack...

Anyone got any suggestions? I cant figure it out!