Computer performance woes

My son is really starting to have problems with the computer we bought for him back in November. Yes, it is a fairly new system, but unfortunately we didn't realize how poorly Vista would run on it because of it not having enough ram. We've thought about removing Vista and installing XP instead, but my son likes many of the new features that Vista offers and doesn't want to go back to XP. We did a complete reformat on his computer this week and at some point within the next couple of days we're going to purchase another memory stick so that he has enough ram to support Vista. That's probably a good thing because it's easier than installing a new OS!