Do you have a Toshiba Recovery Disk?
If not, you can try the following, but, not sure if it works on your model, since it needs a Recovery Partition to work:
Shut down the computer
Next, press and hold the 'zero' key (above the letter 'P') and press the 'power button' once.
When you hear beeping release the zero key.
If it takes you to System Recovery, click Yes to continue.
Select: 'Recovery of Factory Default Software', and click Next.
Select: 'Recover to out-of-box state', and click Next.
Click Next to start recovery.
Also, make sure you save any data you want to keep.
Post back on how it goes.
Retired - Doin' Dis, Dat, and slapping malware.