this is very vague, but would be something that ive experienced on 2 computers iv came across. I think it was a virus, which attached itself to one of the add-ons on internet explorer, and windows prevents internet explorer starting to help protect the computer, If anti virus hasn't detected anything it maybe needs updated or replaced.
if your friend needs internet explorer in the meantime, one without add ons is located in start / all programs / accessories / system tools - internet explorer (no add ons)
Hope this helps