Boot Up Stops

I am using a IT7-Max2 board with a 2.4 Pentium 4 chip. All of a sudden, on
booting up it says the processor is 1.8 and operating at 100mhz whereas it
should be 133mhz. The process stops with a message that there is a mismatch
in the CPU and it should be corrected using the Setup screen. The
motherboard has error light showing 7F.

The solution should be simple: press "Del", get to the setup screen and
change the CPU data through the menu. Unfortunately, it is not possible to
move up and down the menus. The machine is stuck.

Instead of pressing "Del" one can choose "F1" to continue. Then the computer
proceeds to boot up and works under XP, albeit a little slowly.

I have tried clearing the CMOS by changing the jumpers, and reinstalling the
BIOS. Neither makes any difference, and the latter fails saying the update
program does not match the BIOS even though it does match.

Any suggestions on how to solve this problem much appreciated.

Best regards.