if anyone install office 2007 without backup of outlook 2003 mail and that person upgrade MS Office 2003 to 2007 and after installatin when i open outlook 2007 one error msg show "application not found" so plz tell me what should I do.

If i restore my system, problem will solve or not....................it's very necessary for me

So, you upgraded from Office 2003 to Office 2007, and not Outlook 2007 doesn't work? Before resorting to restoring the entire system try re-installing Office 2007 and let it fix any errors that it might find. Make sure you are logged in an Administrator account when you do that.

What version of MS-Windows are you running?