Opera

If you previously installed Opera with the single-user option and after upgrading to Opera 10 have lost your bookmarks, open tabs, or mail, it is possible that the Opera 10 installer has changed Opera from single-user installation to a multi-user installation. This can happen if the Opera 10 installer does not recognize that the installation folder already contains a version of Opera.

You can check if Opera is set to single-user or multi-user profile by going to opera:about. If the "Opera directory" path points to a "profile" sub-folder or your Opera installation directory, Opera is set to single-user profile. If it instead points to a location in your Application Data folder, Opera is set to a multi-user profile.

Your old profile from before the upgrade still exists in the installation folder. To revert to the single-user profile, you must first exit Opera and then edit the file operaprefs_default.ini in the installation folder. Change the line that says "Multi User=1" to "Multi User=0" to make Opera use the single-user profile again.