Ok this isn't really a problem i'm just stumped..

here it is..
I've been running XP on one of my other boxes for months now, anyhow just 2 days ago it started crashing just after booting.
So i thought that it might of been a stuffed up version of XP.
(It does happen a lot with the stuff i do).
Anyhow i checked everything ran system recovery but still the Computer insisted on crashing.
I then asked a mate if he could take a looksie cause i was stumped.
anyhow he suggested that my Mother Board either doesn't like XP or that maybe it just doesn't like the processor that is in it.
(pen 3 - 450Mhz)
So anyhow this is the part that get's me puzzled.
He popped the casing and moved a jumper on the MotherBoard and then Re-Booted the Box, and on the bios screen it said that it was now a pen 3- 300Mhz
Then the next thing i know the damned thing has booted into XP and purring like a kitten again..
So my question is..
How the f**K can a processor can go from 450Mhz to 300Mhz by moving a jumper over to another pin?


f2b:.