I just took apart my computer and its an old computer, i bought PC133 ram a while ago, and i found out i have a stick of PC100 ram in there, would this cause some of my problems of game freezes and such? just curious if i replaced the PC100 with PC133 would it run better and fix my game problems?

Nope! PC133 Ram will run at either 100 or 133 so they are compatible with each other. :)

the 100 or 133 refers to the speed of the bus. It's backwards compatible but will run 'slower'. I however have some 100 ram mixed in with 133 in 133 machines and can't tell the difference.