overclocking is runnign certain components, usually cpu, ram, and grpahics cards, faster than stock speeds.http://dictionary.reference.com/browse/overclocking
you should get the ati radeon 5770 or maybe 5850.
when u open the side panel of hte computer, what does it say on the power supply label? maybe take a picture of it, and use somehting like imageshack to upload it, then post a link here so we know what psu you have .
or just tell us the psu model number :P
\have you tried DRIVEREASY? i just learned about it today, and i tried it out. even the free download version is pretty darn good!