Make sure you understand these basics first.
HT Ref clock x CPU multi = CPU speed
HT Ref clock x HT multi = HT Link frequency
HT Ref clock x Memory multi = Memory speed
(The following may not apply to your CPU, IDK)
HT Ref clock x CPU-NB multi = CPU-NB speed
All of the above speeds are based off of the HT Reference clock. With a default value of 200MHz, we can see that
200MHz x 13 CPU multi = 2600Mhz
200MHz x 10 HT multi = 2000MHz
200MHz x 4 Memory multi = 800MHz (DDR2 800Mhz)
200MHz x 10 CPU-NB multi = 2000MHz
On Black Edition AMD processors, the CPU multi is unlocked. In other words, you can increase it to higher than the default value. If we could increase it to 15, then we get an decent and easy overclock:
200MHz x 15 CPU Multi = 3000Mhz
However, on non-Black Edition CPUs, the maximum CPU multiplier is capped. You cannot raise it beyond what the CPU default is (but you can lower it, more on this later). The only way to overclock non-BE CPUs is to raise the HT Ref clock, as in:
230Mhz x 13 CPU multi = 2990Mhz
But in doing so, since the HT Ref clock is tied to many speeds, we also get:
230MHz x 10 HT multi = 2300MHz
230MHz x 4 Memory multi = 920MHz (DDR2 800Mhz)
230MHz x 10 CPU-NB multi = 2300MHz
Sometimes these results are desirable such as in the case of the CPU-NB, which will show a decent speed improvement when it runs in the 2500-2800 range. Sometimes you won't see much difference, as in the case of the 2300 HT Link of 920 Memory speed over their stock values of 2000 and 800.
In all cases though, we must make sure that whatever speeds we run at are stable and that our temperatures are within spec. Raising the voltage being supplied to these parts is one way to try to make them stable, but you can also damage them by giving them too much voltage. In addition, more voltage means more heat generation, which can be too much for your CPU cooler to effectively remove.
What we can do is lower the multipliers:
230MHz x 9 HT multi = 2070MHz
230MHz x 3.33 Memory multi = 766MHz
You'll notice these are much closer to the stock values and they should be stable without any additional voltages.
Now, the trick is to understand what your BIOS calls these values. Based on this:
HT Link Frequency: Auto (current setting), 200, 400, 600, 800 (MHz)
It seems like your BIOS is already doing the math for you. It's taking the HT Ref clock (200MHz default) and showing you the results of the 1x, 2x, 3x, 4x, etc multipliers. Here's the trick:
Often times what you see are the results of the default HT Reference clock regardless of what you actually set it at. Continuing our example of 230, we should get values of 230, 460, 690, 920, etc. but the bios may not show you that.
You'll have to do the math yourself like so: 1800Mhz / 200 = 9 multi. With a 230MHz Ref clock and a 9 multi we'll get our 2070MHz speed, but we had to choose 1800MHz in the BIOS.
The same thing applies to the Memory clock. It might show you values like 3.33, 4, 5.33. Or it might show you values like 667, 800, 1066, etc. If it's the former, then just multiplier the number by the HT Ref to get the memory speed. If it's the latter, then like in the previous example, assume a default clock of 200 and divide to get the multi. Again, picking 667 MHz (3.33 multi) with our 230 MHz Ref clock will give us a true memory speed of 766.
Some BIOS versions will properly display the results of a changed HT Ref clock, however it should be easy enough to tell if it does because you'll see different values when you change the Ref clock.