With the P4 it is impossible to unlock the CPU.
With the Athlon XP based on the Palimino core you only have to fill the gaps between the L1 bridges and the reconnect them again.
With the T-bred A and B most times the L1 bridges are factory unlocked and the CPU multiplier can be changed. If not close the last L3 bridge.
Motherboards based on the KT400 chipset automatically unlock T-breds even if the last L3 bridge is open.
My PC eats so much money that I'm in 'desperate' need of it to buy PC3500 RAM, help Svol with his OC project!
--- PM me for information.