As I said in your duplicate post...
Not enough information.
One could assume you have Windows XP - but beyond that, what *you* mean by
corrupt is left unexplained. Also - no one knows what happened the day
before, when you first noticed it and what you may have tried to fix it.
Are you getting any error messages? Are you able to boot? I'm guessing you
did not do the basis of good computer maintenance - backups?
Adding to that - what type of external hard drive (name brand of the
drive/drive case, type of drive in the case, type of connection used to
connect to the computer, etc)?
Throw some details out there.