Download a temp program like HWmonitor or coretemp. Then download Prime95.
Go into your BIOS and disable speedstep. I'm not sure of the other Intel features you disable.
Find your multiplier. If intel boards are like AMD boards, it'll be under MIT. Find your multiplier, probably the first one on top that is on auto. Change it until its at 3.5ghz. Save change, exit.
In windows, open the temp program and prime95. Start Prime95, it'll stress test your CPU. Do that for 20 minutes without doing anything else on the computer. If it is stable and doesn't blue screen or give a warning/issue, (Which is won't at 3.5ghz) start all over. Bump it up to 3.6ghz. Repeat until it fails prime95 or until its at a level that you want. If it fails and you want to go higher, given your temps are good, then you'll have to bump up the voltage one step at a time.