tracking what files were accessed

[barefootbilly]

how can I find out what files have been accessed on my computer between a certain time?

little brother is home while I'm at work, I came home halfway through my shift which never happens, the front door was locked (never happens, no one has a key), when I come through the back door I go to my room, find my light on, and my computer off, both oddities.

Any software, or simple XP ways of finding out? cause really I have no clue.