Go into the BIOS (press DEL whilst it is booting).
Go to the Advanced menu (see
here section 4.4) and set it to manual and 100Mhz. Don't worry, as the manual says, if you do it wrong, it will boot up in safe mode any way.
Then save and exit.
(Intel Celeron 900MHz / Socket FC-PGA /
100MHz FSB / 128KB L2 Cache)