Can't Reboot XP Recycles last known configuaration works

When it try to start my computer it does not boot up but goes into a boot cycle. This started happening about two weeks ago. My computer is a Cyberpower with AMD Athlon 1.8Ghz processor. the computer does not load windows completely but goes to the screen that gives me options to start windows in:
Safe Mode
Safe Mode With Networking
Safe Mode With Command Prompt
Last Known Good Configuration
Start Windows Normally.

I can sometime get it to work with Last Known Good Configuration. Today it was even more difficult. Any assistance would be appreciated. I have done a chkdisk and defrag but that did not seem to work.