Until you get the driver issue straightened out (which is a must), this trick which might work:
Turn on the computer and let it completely load windows first then turn on the TV/monitor.
Before my 4870x2 (and the RMAed replacement) finally got swapped out for a working 5870, it was constantly doing the opposite to me with desktop missing the edge of the screen and only properly displaying onscreen with either this trick or setting a custom resolution as CCC had the overscan controls disabled (not an option for you till you can get the CCC running). It had something from the device ID getting fudged due to the sound controller info sent along with the video info on HDMI.
Good luck.
