HELP! somthink wrong with my cf!

Ok, i dont hack and i keep getting a alert come up while im playing crossfire saying speed hack detected, and i dont have any hacks on or even on my pc and my computer had just yesterday come back from the shop (being formated) coz i had a virus what shall i do?!?

-Vet.Risk

u logged off an gone back on?

re-install CF. Thats all i can say lol.