I am having the saamme exact problem, I've tried up[censored] all my drivers, installing and debugging directX9. but I still keep getting the same message.
I have an Nvidea Geforce 6600gt graphics card
3200+ 2.20 Ghz Amd athalon processor
768mb of ram
running on windows xp
80gig hard drive and 180gig hard drive. I have tried everything, down to even the game patches and its all up to date.