PC problem

Aughhhhhhh....frustrating!
My PC keeps shutting down automatically!
It's so difficult for me to work without having to worry about when it will shut down.
If I log out of msn in the midst of a conversation with u, sorry I didn't do it on purpose. It's the PC's fault! *cries...*
I can only get it fixed after my bro has finished his exams at NTU. sigh...