finale wont open a mus file from another program

[erin]

can anyone help? I converted some old music time deluxe files (using finale) to .mus files. Now, finale won't open them saying they are the wrong type. It will open anything i created in finale, but none of the ones which it originally opened in another format and allowed me to save as a mus. Properties of the ones that work and the ones that don't look the sme. Any ideas? Help! Erin