I'm running Windows 7 and have the power options currently set up to put the machine to sleep after 2 hours of inactivity.

Is there any way to force the machine not to sleep between certain hours, or to automatically wake up?

I'm assuming this can't be done directly from within the Windows power settings, but is there a third party utility (preferably free) that could take care of this?

I've got backups scheduled every morning at 3-4am, and these don't run if the machine is suspended, so I just need to make sure that the everything is powered up during this time.