The Opera Password Manager on the other hand is only protecting the data from being entered automatically if it has been set this way. There is no obvious way to look at the usernames and passwords that have been stored in Opera. Tamil over at Opera did post a workaround for that problem.

So the major problem if the Master Password in Opera has been forgotten is that Opera will not fill out the username and password of sites that have been stored in Opera.

Tamil comes again to the rescue by providing a guideline on how to reset the master password in Opera.

If Tools → Preferences… → Advanced → Security → Use master password to protect saved passwords is not enabled, delete opcert6.dat from profile after closing Opera.

If Tools → Preferences… → Advanced → Security → Use master password to protect saved passwords is enabled, delete/rename opcert6.dat & wand.dat from profile after closing Opera.

The process does involve deleting (or renaming) files in the Opera profile directory (located in Documetns & Settings by default). The file opcert6.dat has to be always deleted or renamed while wand.dat only needs to be removed if the option Use master password to protect saved passwords is enabled in Opera.

Please note that deleting wand.dat will remove all stored passwords from Opera Wand.