You might need to start, or boot, your computer using the Windows 7 installation disc or a USB flash drive if you want to:
Install or reinstall Windows 7. For detailed instructions on installing Windows 7, see Installing and reinstalling Windows 7. For information about downloading Windows 7, and then creating a USB flash drive to install Windows 7, go to Installing Windows 7 on a netbook on the Windows website.
Recover Windows 7 from a serious error. If your computer won't start Windows at all, you can access Startup Repair and other tools in the System Recovery Options menu from the Windows 7 installation disc or USB flash drive. These tools can help you get Windows 7 running again. For more information, see Startup Repair: frequently asked questions and What are the system recovery options in Windows 7?
If you use a Tablet PC or other computer with a touchscreen, you might need to attach a keyboard and mouse in order to use Startup Repair and other tools in the System Recovery Options menu.
Turn on your computer, insert the Windows 7 installation disc or USB flash drive, and then turn off your computer.
Restart your computer.
Press any key when prompted to do so, and then follow any instructions that appear.
When the Install Windows page appears, click Install now to begin the installation process or click Repair your computer to access system recovery options.
Follow the instructions.
If the Install Windows page doesn't appear, and you aren't asked to press any key, you might have to specify that your computer uses its DVD drive or a USB flash drive as the first startup device. To do this, you need to change settings in the computer's basic input/output system (BIOS).
Most newer computers can start from a USB device, but some older computers might not have this capability. For more information, check the documentation that came with your computer or go to the manufacturer's website.
Before you change BIOS settings, check the information that came with your computer or go to the computer manufacturer's website. Specific procedures for accessing the BIOS and changing settings can differ depending on your computer's manufacturer, or you might be able to choose which startup device your computer uses without changing BIOS settings.
Be careful when changing BIOS settings. The BIOS interface is designed for advanced users, and it's possible to change a setting that could prevent your computer from starting correctly.
Turn on your computer, insert the Windows 7 installation disc or USB flash drive, and then restart your computer.
Newer computers often display a startup (or boot) menu. On the startup menu, choose "BIOS setup," or "BIOS settings," or something similar.
Procedures vary depending on the BIOS manufacturer. Usually, you must press a key (such as F2, F12, Delete, Esc) or a key combination immediately after you turn on your computer but before Windows starts. If the Windows logo appears, you need to try again by waiting until the Windows logon prompt appears, and then shutting down and restarting your computer again.
The BIOS setup screen appears. On the BIOS setup screen, choose the option called "Boot order," or something similar. Boot order settings might also be listed under "Advanced settings" or something similar.
Select your DVD drive or USB flash drive as the first startup device. (The USB flash drive might be listed under "Removable devices" or something similar.)
Save the setting changes, and then exit the BIOS.
Restart your computer, and then start Windows 7 from the installation disc or USB flash drive as previously described.