I had the same problem. I don't have my A600 put back togather right now or I could tell you exactly how to remedy the problem.
But here goes a wing-ding. Somewhere in the computer's "control panels" folder there is a display adjustment apps that will let you center the V & the H. At least with Worchbench 2.1.
Hope this helps. PM me in a couple of weeks if you don't get it sorted out and I'll have my 600 going again.
