Powerstrip ain't so great
I've been involved with convergence since I first got a SONY CRT RPTV with an RGBHV input about 4 and half years ago. I also bought one of he very first PC HDTV (AccessDTV) tuner cards to integrate with it, so I had adopted HD back when a STB would cost you a cool grand an integrated HD tuners were only a dream. The HD worked fine, when the HD tuner program was enabled, and the HD card sent out its own beautifully scaled output, but when I wanted to use my Big Screen as my monitor directly from my Video Card, that's when I came to understand overscan, and the problems associated with trying to correct it for computer use. I tried everything under the sun with powerstrip to get it to work perfectly with my set, and I was always left with a compromise, not to mention an endless stream of frustration in making settings changes.
While using powerstrip is pretty much the only tool available for correcting overscan on older sets, it's not going to be perfect so accept that from the beginning. If you want the best advice I can give you on this, it is to buy a HDTV that is already designed with an rgb input for this very purpose, rather than trying to get something more out of a TV that wasn't designed to be used that way. Notice the warning given in the walkthrough...not exactly something I'd want to continue using over the long haul if you know what I mean. Use it if you have no other way, but I strongly encourage getting a set with RGB inputs for PC use if convergence is your thing.