Since the 42PE50 native resolution is 860X482 pixels, any signal input with higher reolution than this has to be downscaled with significant loss in detail. That is, text would look awfull and unreadable, images would seem compressed and lacking in detail etc. So the only real choice you have is to switch your computer graphics card resolution to 600X482, or similar depending on your graphics card options.
Furthermore, the 42PE50 does not have a VGA or DVI input. So alternative options to connect your PC to your plasma are:
1. Use the RF output of your graphics card (lousy, unacceptable screen detail)
2. Use the S-VHF output of your graphics card if available (a better solution to the RF output with more image detail)
3. If you have an older AGP series graphics card from ATI (9600 and upwards) you can buy a dongle that connects to the DVI output of the graphics card and converts the signal to component format. You connect the other end to the component input of the 42PE50. This offers the best screen image, and the latest CATALYST drivers from ATI allows you to further play with screen resolutions to better match the 16:9 format of your plasma screen.
4. You can invest in one of the newer generation graphic cards that support HDTV component output. This solution is the same as (3) above, with the difference that you do not have to purchase the special converter.
5. If you wait a few more months you would be able to buy computer motherboards with builtin graphics support that provide output for HDTV screens by means of component connection. Such chips are already being offered by ATI and NVIDIA to computer manufacturers and the first products have already appeared in the market.
However, although it is technically and economically feasible to connect your PC to your 42PE50 you will always be constrained by the native screen resolution of your TV. For casual work - like browsing the net - its ok, but for more serious work you really need a screen that can display higher resolution.