It could well be that your laptop is freezing up after powering back up from sleep mode. You say that you are having to reinstall windows 7. Is this because it becomes corrupted? Have you tried the Acer System Recovery? Have a look at this article which explains this.
When you power it up and nothing happens do you power down and then power back up by keeping the power button pressed down a little longer? Does your laptop have a key(s) to bring it out of sleep mode?
When you manage to get your laptop back up and running have a look at the power option settings and make sure that all drivers have been updated.
Have you tried starting it in safe mode? Press F8 as you are powering up - advanced options - safe mode - log in.