It changes the same in win7 as in winxp."it will not let me do it" can have any number of causes; os should 'present' you with an error or notification or something similar.
Hmmm... i'm not sure about this one... you can try a small work-around for your problem:rename current cameras.ini to lets say cameras1.inimake a new text document, rename it to cameras.inicopy content from cameras1.ini to cameras.ini, do the changes you need, save file.