A quick google search shows that overclocking is limited by Gateway on the bios:http://www.newegg.com/Product/Product.aspx?Item=N82E16883113077
Besides which you would not get much outta the Ph I 9500. If interested in OC'ing, you may want to build you own.
Its possible you could find a modded bios on the web, but since you are unable to get into the bios this would prolly not help much. If you look up your model on gateway's site it should give oinfo on how to enter the bios. You might need to disable the splash screen.
AOD is the best way I know of to OC in windows for AMD processors.