overclocking the i7 is incredibly easy and relatively safe (as long as you stay within intel's specifications). @OP what CPU cooler do you have? If you have a stock cooler, you can still OC, but I would not suggest it as a long term solution since your temps will run higher than optimal.
If you have a good aftermarket cooler, you can make a couple simple changes in the BIOS to achieve a very good overclock. A good starting point on the 920 is 3.5ghz.
The speed of your processor is determined by taking your Baseclock (blck) and multiplying it by your CPU multiplier (defaulted and capped at 20x on the 920). This means that at stock, your CPU runs at 2.66ghz. (stock 133 baseclock times 20 stock CPU multiplier)
Your RAM speed is also determined by your baseclock. You can change the RAM multiplier just like the CPU multiplier. You own the same set of RAM that I do and it is rated for speeds up to 1600 (probably a bit over if you wanted to OC it too...but that can be done later). So, at stock the BIOS should set your RAM multipler to 12x for your rated speed (133 baseclock times 12x ram multiplier = ~1600mhz).
Now that the basics are understood, I can help you with a good set of starting stats to see if you are stable at 3.5ghz.
1). Enter the BIOS and go to the AI Tweaker Tab
2). Change the tweaker settings to Manual
3). Scroll down to the baseclock setting (might be labeled something like frequency...it should be 133 by default) and set it to 180.
4). Go down to CPU core voltage, and change it 1.2v (this is stock, but sometimes the 'auto' setting overvolts your CPU.
5). Go down to the QPI/DRAM voltage and change it to 1.2v (again, this is stock, but just making sure the 'auto' setting does not supply an unnecessary amount of voltage).
6). Go down the DRAM bus voltage and change it to 1.6v
7). Change your RAM multiplier to 8x (any higher will result in a speed higher than the rated 1600, and may work, but this way you guarantee yourself that any instability will not be related to RAM speed). This will be a ram speed of 1440 (180 baseclock times 8x RAM multiplier)
8). Turn Intel's speedstep OFF
9). Turn Intel's turbo option OFF
10). Scroll over to the memory tab and make sure that your timings are set to the rated ones (7-7-7-20)...they will be the first four timing numbers you see.
Save and Exit and boot to windows. Make sure you have realtemp installed. -
http://www.techpowerup.com/realtemp/
And prime95 downloaded -
http://files.extremeoverclocking.com/file.php?f=205
Open up realtemp and begin running a 'Blend' test in prime95. The program is designed to push your CPU to 100% load and does a good job of testing the stability of overclocks. If your computer does not blue screen in a couple of hours, it's pretty safe to say that your overclock is stable (it should be with these settings).
Make sure your temperatures do not exceed 90 during the prime testing (optimally they should be in the low to mid 70s).
I hope that this helps, and feel free to ask for clarification or additional help.