As Mark said if you have anything stored on the Laptop you might need you need to copy it off first as doing a windows factory restore will delete everything.
The Factory restore gives the option to backup before continuing, you will need a USB Hard drive for this.
Then if the laptop still has the recovery partition you only need to press and hold '0' BEFORE and during the power up, this will start the recovery.
If windows is still working a safer way is to make a set of recovery DVD's which you can boot from and recover windows. To do this go to the Toshiba program group and select make recovery media.