Every time I put my computer in sleep mode, it shuts down! What's wrong?

I have an acer laptop and there are options to sleep, log off, shut down and restart. Every time I put the computer to sleep about 15 minutes later you hear it begin to boot up again and a screen shows saying windows was shut down automatically and restart in safe mode or normally. Why does it do this every time? It has been doing it for about 4 months now.

Aase2010-03-07T17:14:02Z

Favorite Answer

control panel>power options change there.

Nomadd2010-03-07T17:37:28Z

Sleep mode is nothing but trouble on half the Windows computers I've seen. Hibernation is worse.
They both have compatability problems with some motherboards. Just don't use them.