The speed you should overclock to depends on your system, over all. The fact that you have an OEM system, with likely a stock cpu cooler, pretty much negates any possible overclocking for you.
You need to research and get as much knowledge as you can here on OCN, and then later build yourself a custom rig with a mobo that has overclocking potential.
Overclocking through the BIOS is the most common way, although there are some programs that allow you to overclock through windows. I recommend doing it through the BIOS though.
Messing around inside your PC has nothing to do with overclocking.
I hope this helps you out.
You need to research and get as much knowledge as you can here on OCN, and then later build yourself a custom rig with a mobo that has overclocking potential.
Overclocking through the BIOS is the most common way, although there are some programs that allow you to overclock through windows. I recommend doing it through the BIOS though.
Messing around inside your PC has nothing to do with overclocking.

I hope this helps you out.