Yes, please check your motherboard* if it is CrossFire certified, and then upgrade VGA driver to CATALYST 6.6 or latest one first, meanwhile, enable this function in the ATI CATALYST Control Center.

* A complete CrossFire system requires a CrossFire Ready motherboard, two CrossFire Ready cards if they are software enabled.

Card One	Card Two
Radeon X1600 Series	Radeon X1600 Series
Radeon X1300 Series	Radeon X1300 Series

* CrossFire Xpress 3200, CrossFire Xpress 1600, Radeon Xpress 200 CrossFire, Intel i955X and Intel i975X based dual-slot motherboards are supported platforms.