erased the settings –> wordpress address (url)

A client of mine went into settings –> wordpress address (url) and deleted the path to his blog. I can ftp in and change the files back but I don’t know what files to change. Anybody know which files he may have affected?

He deleted the settings –> site address

Or should I just see if his host has a backup copy and restore it that way?

Thanks all!
-Jarom