First off, WELCOME TO THE FORUMS!
If you haven't already read this (sounds like you might have read some of it already), the
Overclockers.com Beginner's Guide Section has some good stuff to know about how to overclock, and other helpful hints about your computer in general. One article I think is definitely worth a look is
this one , which was written by one of our Forum Senior Members, Batboy. It is a very thorough article that gives you the do’s and don’ts of overclocking.
Take baby steps... nothing more than maybe 75FSB on your first shot. Boot into Windows and run some sort of processor intensive application or burn-in utility for about an hour, and if it's stable, reboot, and try a higher FSB. Do not try adjusting your multiplier, it is locked, and there's no unlocking it. I think you'll probably end up somewhere around 950-1GHz out of your processor, but be warned, this is basically trial and error. If you go too high and the system will not POST, you must find the "clear CMOS" jumper, and set it so it will clear the BIOS (your manual should have more info on this). This will restore everything to default, but it should let you boot.
You'll want to keep an eye on your temperatures. Make sure they never exceed 50C, and try to keep them below 45C.
If the overclock is somewhat stable, but still gives you some errors on Windows loadup or in the BIOS, you can boost the voltage, but then keep an even closer eye on the temps as that will raise heat.
Also, you might reach a point at which some of your PCI/AGP cards may not work. Most cards can handle up to a 40MHz PCI frequency well, but after that, start to flake out. Be especially careful if you're using a NIC, as these are known to be very persnickety about high PCI speeds.
G'luck, and report back with your max. speed and/or any problems you may have!