Here is solution with ASROCK mainboard k7s8x
I had same problem... Please download www.asrock.com bios upgrade. Make a bootable floppy and copy flash.exe file in bootable floppy..open bios upgrade file , unzip and save in floppy.
upgrade bios to version 2.5. You will be able to install .
boot from floppy. write at flash biosfilename and enter.
you will see message of completion of bios upgrade.
restart pc and goto bios setup..load default settings and make cd rom your boot device. Save and start pc.
And enjoy installation of mandrake 9 or 10.
Khan
bold textbold textbold text