Toshibas usually come with a CD/DVD restore disk !
The way to do a complete reinstall of the system (you will lose everything on it and get back to a "like new" machine) is:
1) While the system is on, Insert the restore CD/DVD
2) Once disc is inserted, SHUTDOWN the SYSTEM
3) Once you turn the system back on and just when the red Toshiba logo appears, access the BOOT MENU by tapping "F12" ( You may have to try a few times as it is tricky )
4) Look for the option that says "CD/DVD", highlight it and press ENTER. The system will be booting on the disc saying "LOADING FILES"
5) Once recovery has started, choose the First Option that will popup.
Recovery will run for about 30 - 45 minutes.
Doing the recovery is just like following a set of instructions, as long as you dont press cancel or no, it will continously load windows on your system.