|Check your online manual, there may be a hidden recovery partition that can perform the Factory Restore. If it is there, you typically need to tap a key or combination of keys during boot up and you go int the Recovery Console and from there, you can launch the factory restore.|
Remember, anything you want to save, do it first.
If the recovery partition is not there, or the recovery console does not launch, then look also into the manual for the method of burning the recovery disk set as riider mentions above.
You have to be a little bit crazy to keep you from going insane.