Insert XP disk, boot to it.
Don mess with the startup repair, I have found it seldom works and proceed with starting a new installation.
After you start the new install, the setup program will run for few minutes and will find that you have a version of Windows installed already and it will prompt you something like "setup has found this version of Windows is already installed" and then it will ask you if you want to do a new install or repair the current installation. At that point, select to repair the current installation. It will basically do refresh install leaving all your programs and settings in tact, for the most part. It is not perfect, but it will be as close to a fresh install as you can get without having to start all over...