Wiping a computer clean and starting over may be the best choice if you have experienced a number of issues with your operating system and if you have performed other troubleshooting methods that have not worked. It is also an attractive option if you are migrating from one operating system to another. When reformatting or wiping your computer clean, you will be deleting all data, programs and settings for your favourite programs.
Back up your personal files, data and multimedia to an external hard drive, USB drive, DVD or other external media.
Insert your Windows operating system installation disc. Restart the computer.
Press the function key required to access your BIOS set-up. (Most computers will tell you which function key you must press by displaying the information on your monitor almost immediately after you restart your computer.)
Navigate to the "Advanced Boot Options" by pressing the navigational keys your BIOS requires on your keyboard. (Your BIOS will display on your monitor the information about which keys are required.)Change the boot order by selecting your CD/DVD drive as your first boot option and your hard disk as your second boot option. This will force your computer to boot from the CD/DVD drive, where the installation disc is, rather than looking to the hard drive for its instructions.
Save your changes and exit the BIOS.
Press any key to boot from your Windows installation disc.
Select the command needed to begin the set-up:
For Windows 7, select your "Language," "Time and currency format" and "Keyboard or input method" in the drop-down menus on the "Install Windows" screen. Click on "Next," then click on "Repair my computer" on the next screen.
If you are using Windows Vista, select "Repair my computer" at the "Install Windows" screen.
If you are using Windows XP, press the "R" key on the "Welcome to Setup" screen.
Click on your operating system if more than one is displayed in the "System Recovery Options" box in Windows Vista or Windows 7. Click "Next," then select "Command Prompt".
For Windows XP, press the number next to your Windows XP operating system in the command prompt screen, then press the "Enter" key. Type the administrator password. If you do not have a password, leave it blank and press "enter."
Type "format c:" (without quotes) at the command prompt. Press "Y" to verify that you wish to erase all data on your C: drive.
Label the hard disk after it has been reformatted if you wish, or leave it blank. (You may rename the hard disk later if you wish.) Press the "Enter" key.
Insert the disc for the operating system you wish to install if it is different from the previously installed operating system. If you're installing the same operating system you've been using, leave the current installation disc in the drive. Restart the computer.
Press any key to boot from the disc. Follow the on-screen prompts to perform a clean installation of your operating system.
Migrate your backed up personal files and data to the new operating system after you have finished the installation process.