PLEASE HELP ME!!

I am satisfied with SuSE Linux 6.4, except one problem:

I'm not able to configure the screen resolution to 800x600 with million colors.

My graphic chip is S3 id 86C391, my OS is SuSE Linux 6.4 with SAX2 and YAST2. Using SAX2 the os detects the chip correctly, but suddendly the configuration test fails, I cannot have any 3D support and the resolution of 800x600 with million colors is a dream for my machine!

CAN PLEASE SOMEONE HELP ME?

I have another pc with same graphic card, running Win 98SE and it works correclty at the higher resolution permitted.