Well your timings in your mobo should be 5-5-5-15 (or VERY similar).
Overclocking RAM is VERY easy,
In your BIOS locate RAM Frequency, and it should say 333.
Your computer multiplies this by 2 to = 667 MHz.
First try increasing the number to 400MHz (giving you 800MHz speed), and save and exit.
If your computer starts, it should, you're good to go.
You can try and DECREASE the times to 4-4-4-15, if that works then try 4-4-4-12.
A couple of notes though:
1. Trying both may not work, but its worth a shot.
2. If your overclocking your CPU too, there is a GOOD shot that it will make your computer unstable.
ESPECIALLY if you decrease your timings.