If the system will not start in Normal Mode or Safe Mode

A Windows XP system that will not start in Normal or Safe Mode is not a good sign and may be the result of corrupt or missing system files, a corrupt registry, hardware drivers or failed services. Your first step is to press F8 during Startup and select the Last Known Good Configuration option from the Windows Advanced Options Menu. If Windows boots normally, check the event logs and hardware manager for clues as to what may have caused the failure. You may also want to check the Add/Remove Programs menu for any new applications that may have contributed to the failure.
If you are unable to determine if a driver or service is responsible for the startup failure, you should run the Checkdisk utility from the Recovery Console by typing CHKDSK at the command prompt.
.If you are still unable to determine the cause of startup failure at this point, you have the following options:
1. Use System Restore to return your critical system files and some program files from a previous restore point. I've had mixed results with System Restore, but at this point, it is still worth a shot. System Restore can be activated from the Recovery Console. The advantage of using System Restore is that your personal files located in My Documents will not be overwritten or deleted. More information can be found in Microsoft Knowledge Base article 306084.
2. Restore from a backup tape: While this method will recover your system, you will lose any data stored on your workstation that was created after the system was backed up. This method will also not help you identify the root cause of the startup failure, which may occur again.
3. Perform an in-place upgrade (reinstallation): This process reinstalls the operating system but may result in data loss if not done correctly. The advantage is that it should return the workstation to a bootable state in which important files can be copied. Applications, service packs and system updates may need to be reinstalled for the system to function properly. For more information, see Microsoft Knowledge Base article 315341.
4. Perform a parallel installation: A parallel installation involves creating a second Windows XP installation on the same workstation, either in a new folder or on a secondary (slaved) hard drive. The advantage of this approach is that it allows data to be recovered on the primary drive, assuming disk failure was not the cause of the startup issue. After any critical data is recovered, the original installation can be restored from backup source and updated with the new files.

Note If the Chkdsk command reports that it cannot gain access to your hard disk, you may have a hardware failure. Examine all cable connections and any jumper settings on your drive. For more assistance, contact a computer repair professional or the manufacturer of your computer.

If the Chkdsk command reports that it cannot fix all hard disk problems, your file system or Master Boot Record (MBR) may be damaged or no longer accessible. Try appropriate Recovery Console commands such as Fixmbr and Fixboot, contact a data recovery service, or repartition and reformat your hard disk.