"Mercenaries 2: World in Flames is unable to continue due to an error

initializing your graphics hardware"? System specs :
Processor : AMD Sempron(tm) Processor 3000+, MMX, 3DNow, ~1.6GHz
Vid card : ATI Radeon HD 4800 Series
system : windows XP


This used to run on my system, but now it doesn't, anybody help with this? my graphics card is brand new, so don't tell me to replace it.