Video Resolution Problem on RH7

I have installed RedHat Linux 7.0 on a Pentium III with a S3 Trio3XD/2X video card. After installation and booting into graphical user interface my mouse cursur was a large white square.
Then I went into setup and started XConfigurator and went through the process of configuring the XServer again. This time the cursor problem is soved but the resolution is 320X200.
Does anyone know what is wrong and how I can resolve this issue?