To reinstall Windows or access repair tools loaded on your Windows DVD, you'll need to boot the PC from the optical drive instead of the hard drive.
- Insert the DVD with Windows running, and then reboot.
- Watch the on-screen text carefully during boot time, and press the correct key when you see 'Select Boot Device', 'Change Boot Order', or another similar instruction. The key will likely be Esc, F10, or F12. If you miss it--you have only a second or two to act--reboot the machine and try again. Don't worry about mashing on the key.
- Once you're in the menu, choose your optical drive by using the arrow keys, and press Enter.
- Keep waiting. You will soon see a message that reads 'Press Enter to boot from CD' (or something similar). If you don't press the right button at this point, the system will proceed with booting normally from the hard drive.