Hi my motherboard allows me to unlock cores on my phenom quad processor shall I? Also overclockinh worth it?

Yes, and yes. Provided you've got a good cpu cooler and your ram can hack it.

Ok got a good CPU cooler and 8 gig of cosair ddr3 ram on the selection of core overclock it has a few options manual, auto, docp, CPU level up overclock profile and test mode any idea, also what is it safe to overclock to? It's a 3.4ghz black edition.

What motherboard is it? I mean test mode should effectively be that - testing to see whether it works...

As for how far to go - easiest method is to do auto if you're unsure - You could always google the model number of your black edition and see what others are getting out of it - CPUID is your friend for serial numbers to see what others are getting and the settings they're using

It's changing the voltages and Other changes that I'm bit sure!

Have you googled an over clocking guide for your CPU/mobo? If it's a fairly normal combination there will probably be something telling you voltages Etc.

Like I said - CPUID is your friend - Then once you've got the serial number you can drop it into google and work out what overclocks people are getting at what voltages...

Most people can core unlock without any other mods - OC'ing is a little more work but nothing that most people can't handle.

And if OC'ing fails - clear cmos and try again

I presume I change it all at the bios, I changed I few things on amd overdrive, an overclocking programme but on the bios it's telling me it's still running at 3.4ghz when apparently I've changed it to about 3.6.

amd overdrive overclocks it AFTER the system has booted. Doing it in bios does it before the system boots. When you do it is irrelevant really...

If you've unlocked cores and are comfortable with amd overdrive that's probably best for you. bios offers extra features and control that amd overdrive doesn't usually.

Just remember that the unlocked core may have been locked off for a reason, some of them are OK, but others can be unstable, even at standard speeds; my PII wouldnt give me a stable unlock. Also be aware that unlocking a core increases the heat the cpu puts out, sometimes it is better to leave the core locked and go for a higher overclock with the original cores, especially if the programs/games you use cannot make use of the extra core(s).