You could try a repair, at least to get access for file recovery.
Repair Installation Instructions
or
How To Run A Repair Install
(How to Repair Windows XP by Installing Over top of Existing Setup)
All you do is boot from the CD. When it asks if you want to repair and to press "R", don't. Continue with the installation just like you were installing for the first time.
You will then get a license agreement and it will ask you to press F8 to agree. Right after that screen, you will see a list of Windows installations that setup found. It will ask if you want to repair it. Read the directions on that page!!!
Then, you will actually press "R" this time and XP will re-install.
When done, you will be back to your familiar desktop with everything looking just like it did before. But all your Windows Updates are gone and you will need to get those again.
If you have any problems booting from CD, set the CD to boot earlier than the hard drive in BIOS setup, or come back for more help. If you don't get the "Repair" option to press the second "R", then your registry is too damaged for a repair and you need to restore an earlier copy of the registry.