1. Start up your computer.
2. Immediately insert your Windows XP install CD. As the computer boots, a boot menu will appear (if you did not insert the CD in time, you will not see the menu; in this event, simply reboot the computer again).

3. Select the option to boot from the CD. A setup screen will soon appear.
4. Press the 'R' button on your keyboard at the setup screen in order to open the repair console.
5. Type in the administrator account's login password if you are prompted to do so. If there is no login password, simply leave the password slot blank and continue. After this step, a command prompt will appear.
6. Type in 'chkdsk' (minus the quotation marks) and press 'Enter.' Allow the operation to run.
7. Type 'Exit' (again, minus the quotation marks) when the operation is complete, and press 'Enter.' If your computer boots correctly, great! If not, move on to the next step.
8. Reboot and repeat Steps 3 through 5.
9. Type 'fixboot' (minus the quotation marks) and press 'Enter.' Once it is complete, repeat Steps 7 to 8.
10. Contact Windows Support if the issue is not resolved. You might need to reinstall your operating system.