Just wondering if it is possible to increase the stock fan speed on a e8400.
If it's at full speed (100%), it's full. The motherboard bios won't normally let you overvolt fan to make it spin faster. Although you can disable speed control in bios to make the fan spin at 100% all the time, instead of only when the cpu heats up.
Ideally, get an aftermarket cooler:http://www.frostytech.com/top5heatsinks.cfm