Games freezes after replacing new video card

Hey I have a question. I recently bought a 128mb64 bit 8x speed video card for my PC in which earlier I was using a 64mb card. Well my problem is that after installing the new card my PC gets stuck while playing games like command and conquer generals. I think it is related to the video card because earlier I didn’t have such problem with my old one.
Between I have a Pentium3 650mhz computer (an old and reliable system) and the cards I am talking about, both go into the onboard 2x agp slot.
Also the PC gets stuck mostly in games not in programs.
