The instructions for my Toshiba Satellite has this in the User Guide:
Restoring the pre-installed software from the Recovery hard disk
drive
A portion of the total hard disk drive space is configured as a hidden
recovery partition. This partition stores files which can be used to restore
pre-installed software in the event of a problem.
If you subsequently set up your hard disk drive again, do not change,
delete or add partitions in a manner other than specified in the manual,
otherwise you may find that space for the required software is not available.
In addition, if you use a third-party partitioning program to reconfigure the
partitions on your hard disk drive, you may find that it becomes impossible
to setup your computer.
1. Turn off your computer.
2. While holding down 0 (zero) key on the keyboard, turn on your
computer.
3. A menu will be displayed from which you should follow the on-screen
instructions.
System Recovery Options
The System Recovery Options feature is installed on the hard disk when
shipped from the factory. The System Recovery Options menu includes
tools to repair startup problems, run diagnostics or restore the system.
See the Windows Help and Support content for more information about
Startup Repair.
The System Recovery Options can also be run manually to repair
problems.
The procedure is as follows. Follow the instructions shown on the onscreen
menu.
1. Turn off the computer.
2. While holding the F8 key, turn on the computer.
3. The Advanced Boot Options menu will be displayed.
Use the arrow keys to select Repair Your Computer and press
ENTER.
4. Follow the on-screen instructions.
The System Recovery Options feature will be unusable if this partition is
deleted.
The Windows 7 CompletePC Backup feature can be used on Windows® 7
Professional and Windows® 7 Ultimate.