How to Perform a Windows XP Repair Install Repairing a Windows XP installation can be ideal if you are having problems with your current installation of Windows XP. This repair will allow you to keep your current documents and applications intact but will reinstall Windows XP.
Please Note: This is not the same as a format and reinstall of Windows XP and is a lot less time consuming. Please Note: As you are reinstalling Windows XP you will also need to reinstall any Windows Service Packs and Window Updates. Your documents and applications should remain intact and they will be available to use after the repair has completed.
If you are experiencing difficulties with Windows XP then you may find it necessary to reinstall Windows XP. However a reinstallation of Windows XP can be time consuming. Therefore you may wish to consider a repair installation; as it's quicker. As you will be reinstalling Windows XP it would be advisable to make the appropriate backups of your documents, favourites, music in the event that something did go wrong.
To repair an installation of Windows XP you will need your Windows XP - Installation Disk. Place this disk into your CD/DVD Drive and restart your computer. Now you will need to set your computer to boot from the CD/DVD drive.
The following is how to repair an installation of Windows XP...
1. When you boot from the CD you will have to Press any key to boot from CD.

2. Now your computer's hardware configuration will be inspected.

3. The Windows Setup will now load all files that are needed.

4. Repairing Now as we are Repairing Windows XP press ENTER.

5. Now you will have to accept a License Agreement to use Windows XP, so press F8 to Accept.

6. The Windows Setup will then look for previous versions of Windows.

7. Now as we are Repairing Windows XP press ENTER.

8. Now files should be copied to the Windows XP installation folders.

9. Restarting Your computer will now be restarted in 15 seconds.
However by pressing ENTER you can force a restart.
Once the computer has restarted Windows XP will continue to install. Once this installation has completed you should then install any Service Packs or Windows Updates. You should also find that your documents and applications have remained and you can continue to use your computer as normal.

At this stage you’ll need to reapply some of the settings that the repair wiped out, such as your time zone, your network settings, etc. Just follow the easy prompts and you’ll be back on your way.

This is the screen where you set up your workgroup or domain. If you are not in a business environment, then most likely you don’t have a domain and you can just click next and leave workgroup selected.

More installing.

When done your computer will reboot. Just wait for the computer to start up.

The Welcome to Microsoft Windows screen appears next, informing you that the next few minutes will be spent setting up your computer.

Registration with Microsoft is optional, but if you’d like to do that now, choose Yes, I’d like to register with Microsoft now, click Next -> and follow the instructions to register.Otherwise, choose No, not at this time and click Next ->.

In this step, setup wants to know the names of the users who will use Windows XP so it can setup individual accounts for each user. You must enter at least one name but can enter up to 5 here. More users can be entered from within Windows XP after the repair installation is complete.

Thank you screen appears, just click next.

Welcome to you repaired version of Windows.

Summary...
This is all that is required to repair an installation of Windows XP. Repairing an installation is a lot less time consuming then reformatting and reinstalling. You also have the benefit that you do not need to install any applications and your documents will remain where they were. If you find that you are experiencing problems that are proving difficult to solve you might want to consider a repair installation.
If you do decide to repair your installation of Windows XP then you might have a problem updating Windows. To resolve this issue please take a look at the Summary...
This is all that is required to repair an installation of Windows XP. Repairing an installation is a lot less time consuming then reformatting and reinstalling. You also have the benefit that you do not need to install any applications and your documents will remain where they were. If you find that you are experiencing problems that are proving difficult to solve you might want to consider a repair installation.
If you do decide to repair your installation of Windows XP then you might have a problem updating Windows. To resolve this issue please take a look at the
Microsoft Knowledge Base Article: 943144. source