If youve bought it lately then yea its locked and there isint anyway to unlock these chips.
You will have to overclock using FSB. Have a look at the overclocking guides, depending on your cooling you should stick to a Vcore limit. Ie generally people say under 1.8v with med air cooling, good air 1.85-1.9v , water cooling 2v.......... thats generally MAX btw but different people ahve different limits.
Divertas, look on your CPU for the stepping code(this will require you to take off the HS and remove the CPU), there should be 3 sets of numbers and letters. Example:AXDA2400DKV3C Z330784270389 AIXIB0337SPMW. To determine if your CPU is locked or unlocked look at the second set of the stepping code at the 6th thru 9th number. My example is 0337, if those number read 0339 or BELOW you have a unlocked CPU. If they read 0340 or ABOVE, you have a locked CPU.
There are a FEW locked CPU's that can be unlocked, but most are now SUPERLOCKED and can never be unlocked. You will have to do some research on your stepping code(if it is locked) to determine if your can be unlocked, but dont count on it.
Im interested in this as well as I'm buying an unlocked XP2000 (palomino) from a friend for $25 to replace my XP1500. I've only got PC2700 Crucial ram, but I would like to know how far a usual overclock can go. If I could match a 2500 I'd be very happy.