Hmmm, I had that exact error due to an XP system crashing so often. I did a manual repair of the registry on that machine, but I thought I remembered getting back to desktop to do the manual repair by repairing the boot sector first. Maybe not, but that 's if I remember correctly. I eventuall reloaded that computer and found the reason for all the crashing leading to registry corruption. A bad SATA cable. Fixed and running today.
EDIT: With this particular error, a repair of the corrupted boot sector will get you back to desktop, but...it will not permanently fix the problem.