You see an application popping some text on you and you wish to find which among the many dlls and executable that string is coming from.
Surely many ways would be there.
Today a friend of mine suggested use of 010 Editor for it.
010 Editor -> Search -> Find in Files
Put the directory path where you would like the editor to search dlls and exe for your string. Choose among the various formats like ASCII/Unicode/ANSI for the string and go ahead.
It helped me; might help you some day. Cheers!