if you have 768mb of ram i assume you have 1 512 and 1 256. is that right? if so that's not good. Your ram is gonna work only as fast as it's weakest link, being the 256. so you are actually slowing down your computer by mismatching. if is capable of 4 gig then go to crucial, buy the ram and do it the right way. you should be able to get 4 gb for around 30 bucks.