My computer won't hibernate!

Hello!

I'm posting this because my computer simply will not go into hibernate mode.
I'm running XP Home Edition, and my current Power settings are as follows:

Screen saver: 15 minutes (no password)
Turn off monitor: after 30 mins.
Turn off hard disks: after 1 hour
System standby: after 2 hours
System hibernates: after 3 hours

And yes, the "Enable Hibernation" check box is checked under the "Hibernate" tab as well.

I've even reinstalled Windows XP, and it's STILL not going into hibernate mode.

My monitor will go into power save mode after a while, but no matter how long the system idles, the computer will just sit there and run like normal. As soon as I touch my mouse, the monitor kicks back on and it appears that the system is still going along as if nothing happened.
I'm trying to conserve some power here, and also trying to get my compy to go to sleep without having to turn it off and on when I don't want it running (like when I'm trying to sleep!) Can anybody help me?

Thanks!