Wake the PC from sleep/hibernation when power comes up

I live in a place where we have power shortages from time to time. I have my Dell desktop pc attached to a UPS and i have configured the pc to go to sleep after 5 minutes when on UPS. Is there anyway to wake up the pc automatically once the power is on? I have connected my UPS with USB cable to the pc, and the pc treats the UPS as a battery. I use this pc as a media centre so this feature is something i really need.
I am on Windows 7 Ultimate.

Thanks!

With it being a Dell the option may very well be hidden (with no way to unhide it), but have a look in the bios under the Power options for anything relating to "restore on power loss". If it is there it is likely set to disabled (the default on most if not all motherboards), set it to enabled and that should do it.

Under Power Management in BIOS, i tried setting the AC Recovery to ON ("System powers on after AC power is restored") and it did not turn the pc from sleep and it did not work in hibernated state either. This worked only when the pc was completely off and when i connected it to AC, it turned on automatically. It does not seem to do the same when the pc is on Sleep or Hibernation mode though.
I also set AC Recovery to Last ("System returns to the previous state after the AC power recovery") and it did not work either.

Does anyone have some other suggestions?

I was able to kinda solve my problem. I created a .bat file with "exit". I than created a task that will run indefinitely after system start-up and will execute the above command every 20 minutes. I also told the task to run itself only when it finds a network connection, and i modified the task to wake the system to run this task. Since my pc and router are on the same power network, this is exactly what i needed :)