Core Unlocker is a feature which comes with the ASUS 890GX boards. If you had put in say a Athlon II X3, Phenom II X2 or Phenom II X4, some of the cores are 'locked' - either because they were defective during the manufacture or because they wanted to sell more dual or triple cores. It unlocks a Athlon II X3 to an Athlon II X4, and a Phenom II X2/X3 to a Phenom II X4, however, it may not work sometimes as the core may be unstable or fully defective. To use it, all you do I think is just move the Core Unlocker switch to the 'Unlocked' position.
Overclocking is when you run a processor at a higher speed than it originally comes with, for example, running an AMD Phenom II X4 945 at 3.8GHz, when default it runs at 3.0GHz. This is done to increase the speed of the processor, thus boosting PC performance. However, overclocking can be dangerous - if the temperature is too high due to the increase in speed and or voltage, the CPU could be potentially damaged.
As for Windows 7 TRIM - it is a function which helps increase the longevity of SSDs, which have limited read/write cycles. I'm not exactly sure how it works though.
Edit: If you meant unlocking cores like HIB suggested, all you need is a motherboard with a SB710 or SB750 SB. Just look at HIB's list, and also add some 740G, some 760G and some 780G northbridge-based chipsets.
Some motherboards will have "Automatic Clock Calibration" in the BIOS which should be set to Enable. But that is not all, it combines with "EC Firmware" that you have to set to special. MSI motherboards have "Unlock Core" in the Cell BIOS, the most direct way possible.
Beware of ECS motherboards. I heard that some model that have the above chipsets do not have unlocking feature. 890 motherboards also do not have unlock as basic. I know ASROCK does have the UCC: http://www.asrock.com/mb/overview.asp?Model=890GX%20Ext...
If you are interested in unlocking cores, review the motherboard carefully and check customer reviews in Newegg for testimonies of successful CPU Core unlock.