No problem ;
TO stress the processor there are many application the most popular is prime 95 (it s dual core version is called ORTHOS ) . This software stress your processor with many mathematical calculation and push it to 100% load . Such software are usually used for stability testing after overclock . If the software run for 12-24 hours without error then the system can be considered as stable .
I've always used prime 95 (or ORTHOS) for my stability testing. While 12-24 hours will guarentee you a stable system, sometimes you can get away with only a couple of hours tested for a higher overclock.
Usually you do want to do the full 12-24 hours though.