Personally, I have always found that sleep mode can cause no end of bother and NEVER use it now. Others may say they they never have problems, then, good luck to them, but its not for me.
I used to feel that way, but not with Windows 7 and it's Hybrid sleep mode which is "almost" problem free. There are times, typically after some update, where my system refuses to go to sleep and that is typically due to something that is still running.
For example, I am addicted to Spider Solitaire. If I walk away after winning and leave the fireworks celebration display "running" (which includes sound) my monitors will go to sleep but not the computer. As soon as I close Spider (or start another game to get rid of the fireworks sound bites) I can have Word, tons of open browser windows, and just about anything else, and my system will sleep. And Spider is a Microsoft program!
So check to see what you still have running (including in the System Tray) and see if something there is not the problem.
The only other time I have problems is, on rare occasions after an update, it will not go to sleep. Some times, a simple reboot fixes all. Other times, I have to change the sleep settings and change them back. For example, if set for 15 minutes, I will change it to 10 minutes - hit Apply - then change it back to 15 and hit Apply again.
In any event, I strongly recommend Hybrid sleep mode for
PCs (NOT notebooks) running Windows 7. See
here to learn how to enable/disable.
