512 reading as 448

My friend has 1 512MB stick of Compaq RAM in his comp but in windows it reads as 448 and it seems to actually be affecting his computer's performance. Any help ro solutions?

Maybe he is sharing the memory with his onboard video card?

Yep, the rest is being used by the onboard video. The only way to get it back is to turn off/reduce the shared memory for the onboard video. Which I highly recommend not doing.

64MB of that ram is being taken by his onboard video card. He could go out and buy a video card (they are cheap) and disable the onboard video, which will free up that RAM, but then again, if he's happy with the video and is not a gamer, that 64MB won't make much of a diff, he may as well go out and buy another stick of 512MB ram and be happy. He'll still be -64MB but it won't be noticable (however, 448MB and 512MB can be noticable since 512MB is already on the borderline and is the recommended minimum for XP (the absolute minimum is 256MB but you don't even want to try running that)).