Thank you all for your support after loading default settings of bios now its showing my processor information as before. I think all this problem started when I connected my front panel USB panel to wrong portof MB. My system wasn't booting up and started to shut down in 15 sec after powering it on. May be at that time I chose 4 core enable option. Now after loading default settings of bios every thing is fine. Once again thank you all for your support.
Oh, yeah that must have been it!
If you want to re-enable it, then I recommend doing some research on it. I've never learned anything about this because I'm more into Intel, but I see a ton of people unlocking theirs over on Overclock.net.
Also known as core unlocking,
How AMD Core Unlocking Works | bit-tech.net
Unlocking Athlon II / Phenom II cores and L3 cache
and for the most part is perfectly safe as long as the unlocked core(s) is stable. On some of the CPU's the core(s) are locked because they are defective, on others they are locked to fill demand for that type of CPU (x2, x3). It is also a way to get a better CPU (more cores) for less.
Only way to find out if the unlocked core is stable is to test it with stress test or gaming even. If it is you can leave it unlocked and use it as a quad core instead of a triple core.
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