I was going to suggest one of the NFS games, but it might be over-complicated for a 7 year old.. go to your nearest EB games (or other store) and look into those bargain bins they got or general electronics stores, that have that one revolving thing with older pc titles. That's all I got..
I would suggest Need For Speed 6 - Hot Pursuit 2. This was the last game before all the hideous "tuner cars" took over the series. It is fairly simple gameplay, involving time trials and outrunning cops, etc. As the player beats more events or single races, he gains "money" to unlock more tracks and cars. I always enjoyed this game the best, and I know for sure it runs on Windows XP, and likely won't take a supercomputer to run. I ran it on high details on a Radeon 8500, so I'm guessing any modern Intel chipset shouldn't struggle.