Problem Upgrading from Dead Video Card

I just installed a new geforce video card after my old one had died. The problem i am having, is that anytime i attempt to play a video now, media player and my entire system itself hangs.. and the mouse arrow will occasionally move for a split second and then freeze. and it repeats this behavior until i get so frustrated i have to manually reboot my pc. After having read various threads about upgrading video cards, i have come to assume that this may be a result of not having removed the old drivers before i installed the new ones. My question is: Is this most likely my problem? And if so.. How do i go about fixing it? Any opionion on this matter would be greatly appreciated. Thanks.