First and foremost, in order to take full advantage of your ATI card, you'll need the ATI drivers found on the ati website
. This can be much easier said than done, and I suggest you look at this website
Having said that, your xorg.conf looks wrong here:
DisplaySize 380 300
ModelName "PROVIEW MONITOR"
I expect the display size line could be removed, but failing that, I would suggest a more ideal:
DisplaySize 1024 768
or if that doesn't work, a more traditional:
DisplaySize 640 480
I could be wrong though, and you should be sure to back up your xorg.conf (in case you didn't already know). All you need to do is rename is xorg.conf.old or something.
Another possibility is the horizontal and vertical refresh rates. Have you checked them against your monitor's documentation?
The only other possible problem in that section is the UseModes "Modes" line. I have no idea what it is or does, so you may want to search around.
Let us know if this helps