System Event Logger?

Hi, I'm new to Mac Rumors so go easy on me?

I had a document on my iMac which had sensitive information on it. I never thought to password protect it. Anyway, someone questioned me about it today after they had used my Mac, and I think they copied it onto their memory stick. I know it's my own fault for not securing it properly, but that's passed.

Is there any kind of application on Mac OS that lets me view events that have happened on my computer? It was in a different log-in session, and the computer has since been shut down. Running the latest OS by the way, 10.6.6

Thanks in advance for help

 

brilliant, thanks for the quick reply. Unfortunately I swear I don't know half the things my Mac can do

 

thanks for the replies, but i'm a total novice. do either of you guys know what i am looking for? It just all seems to be error messages