Juubjuubcow 0 Newbie Poster

Ok so...Ive had this problem for about 2 months...
I have an NVIDIA 6600 GT and its got problems...
When I play any game on my comp the graphics flash red/green/purple..I belive its called artifacts...
Please how can I remove them!!
Ive uipgraded my power supply from 250w to 500w...it did not work...
Please please help, I dont know what else to do...