Powerstrip won't help - it can only control the signal being sent from your video card's RGB/DVI connectors.
Almost all PC video cards have some sort of converter/transcoder chip that takes an incoming resolution from the video card and converts it to a TV signal (often rather poorly). The controls for these video-out devices are device specific.
All you can do is download the correct driver for your particular video card, and use the tools supplied with it to control the video signal. If you have a decent quality Nvidia or ATi card, these more often than not have some sort of over/underscanning control. This will be your best and cheapest shot.
As a last resort, you can try something like TV Tool:
http://tvtool.info/index_e.htmAlthough active development and support seems to have stopped for it. I would try official video card drivers first.