Why is my computer now going to sleep?

[Kickin' Ass and Takin' Names]

For some reason, my computer has started going to sleep.

Previously, if I left it running for a while, the screen went blank.
If I moved the mouse or hit any key, I could hear the HD spin up, the
monitor would come on, and I'd go back to work.

Now, it's starting going into a hibernate or sleep condition.
Sometimes if I move the mouse or hit a key, the monitor will come on
and everything's normal. However, most of the time, if I leave it
turned on and come back in after more than a few minutes, the power is
still on but screen is blank. Nothing happens if I move the mouse or
hit a key. If I push in the power button and hold it in for 10-15
seconds, the computer turns off and I can turn it back on.

I went to Start > Control Panel > Power Options and turned off the
hibernate stuff -- any suggestions?

 

[Bob I]

What changed between then and now? Also the BIOS sometimes has the
ability to do "power management".