Go here: http://www.cpuid.com
Download CPU-Z version 1.29. See what your multiplier is. Also see what your core clock speed is for your processor. Look at the FSB too. This all helps determine what your multiplier should be at.
Let's say your core speed is 1300 MHz and your multiplier is 13 and your FSB is 100. 100 x 13 = 1300. Easy to see where the numbers come from. Now, by upping the FSB, you can start to overclock. However, there is a maximum core speed for your processor. Now, if your FSB is at 100, but should be at 166, you'll need to fiddle with your multiplier too. Just quickly calculate what your multiplier will need to be for certain speeds to get it to 2000 MHz. Do one at 133, and one at 166, or whereever else you need to calculate for.
2000 / 100 = 20 (There is no way you'll have a multiplier of 20, which is why the FSB need to be raised)
2000 / 133 = 15
2000 / 166 = 12
So to achieve a FSB of 166 and a clock speed of 2000 MHz (or 2 GHz), you'll need a FSB of 166 (obviously) and a multiplier of 12. That will get you close.
Now when you do this, you should go up slowly and see what happens. Since you CAN handle 1.3 GHz, raise the FSB without changing the core speed until you get close to 1.3. So, for the first step of 133, claculate what you need to keep the processor around 1.3 GHz. 1300 / 133 = 9.7 (make it 10). Now when you hit this point, you should have a speed of 1.33 GHz. Now slowly raise the multiplier until you get as close to 2000 as you can, but only go in small steps.
133 x 11 = 1463 (keep going if this is stable)
133 x 12 = 1596 (keep going if this is stable)
133 x 13 = 1729 (keep going if this is stable).... you get the point, but do not go over 2000 MHz yet.
When you get your highest number, and know that it is stable there, it is where you'll want to work from for the next part. (for the sake of this example, we'll use 1729). Now divide it by 166 to see what you need to decrease your multiplier to for the next jump. 1729 / 166 = 10.4 (round to 10). Now raise the FSB to 166, and the multiplier to 10 and see if you're stable. You should now be at 1660 MHz. Slowly raise the multiplier again until you get the speed you need.
Remeber, that was an example. You have to use your own numbers to put it in. If your FSB is already at 166, then you'll need to increase the multiplier. If you increase the FSB, remember to watch the RAM also and make sure that doesn't go too high (you may need to resort to dividers).