Display settings

When I booted up today my system would only display 16 bit color at 640 x 480. It will not allow any other setting nor are any options listed. I have tried changing it manually and rebooted several times. I went into safe mode to look for errors andalso in “systems” under the control panel but saw nothing. Do it need to reinstall Win98 since I have rebooted several times and probably the old settings have already been erased or changed?