Ok i will teach you about overclocking. See my signature - i do it myself.
Ok, make sure you have a brand named PSU that will easily take changes in voltage and has some kind of voltage protection.
Make sure your CPU temperatures are good at idle/full load at the moment.
Make sure you have RAM with availiable MHz (eg at least PC3500 DDR433 for a 400MHz athlon/800MHz P4)
You will probably be best overclocking in BIOS.
What you want to do is set the AGP/PCI ratio to fixed at 66/33 - the speed it should default it at - lock it there.
Increase the FSB of your processor by one or two notches, save and exit, see if it loads windows. Run prime 95 for half and hour, if it dosent error, repeat.
Only do this if you know what you are doing!
And for the graphics, use Rage3D tweak. Its very good. Don't push it too far though otherwise you screen will be al blocky and liney and illegible
Chris