Looks like you use the wrong drivers.
Uninstall them and go back to the standard VGA 640x480 setup from Windows.
Then rightclick anywhere on your desktop, select Properties and go into Settings and then Advanced. In there, click on Adapter and then Properties. Now click on Driver and Update Driver.
Now make sure to install the Sis630 drivers, not the Sis300.
I don't know XP (use W2K myself), so maybe not all my tips are correct.
If you can update the drivers by running the downloaded driver-file, do that instead.