If you Google "Autocheck program not found" you will see this mean a particular file (autocheck.exe, surprise!) is corrupted. There is a MS KB article (
913502) on how to fix it by copying the file from the install CD. Doing a repair install would be overkill if that is the only problem.
That said, corrupted files are bad. They just do not happen very often on systems that are in good working order, especially on system EXEs as opposed to data files. I suggest you invest in a good backup system very soon (but I do suggest that to anyone who does not have one). If the drive is off warranty I would just replace it and reinstall the system. If that is not an option then do some research on the freeware that is available for checking and maintaining drives. This drive may be usable for a while (even a long while) but I would not depend on it.
I also booted a PC from a Windows XP in tall CD that only had an unpartitioned drive in it. The installer did not give me the option to repair the installation. I have no idea how the installer decides if there is something on the disks that it thinks it can repair. There has got to be a bunch of different ways they could do that. Maybe it looks for autocheck.exe.
Next test... I booted a computer with Windows XP Pro installed from and full retail XP home CD and did not get the repair option. Does this computer have Pro or Home on it? Did you install it from the discs you are trying to use to repair it?