nvidia keeps crashing can it fix?

sorry for posting agien i didnt see this topic**

hello guys External Image i was woundering why is my nvidia video card always crashing when i play games?these green lines come up and then a blue screen comes up saying"nd_4.dll has stoped working unexpecticly to prevent damage the computer will now restart".the symtoms are a green line come all over the monitar and the game crashes.sometimes there little square green dots or line that are green. oh ya and im using nvidia geforce 7300 GS.how do i fix this anoyying problem.im scared to bye a new nvidia video card because this problem might happen agien. this prevents me from playing video games PLEASE what do i do