Strange error message

[happyturk]

Lately I've been getting an error when I get through the intro and into the playable part of the game I'm writing:

That is the wrong disk. Please insert disk 1 and press Enter. Press Esc to quit.

...and unlike most of the problems I have, I don't even know where to start. I have no idea what could be causing this error when it never happened before- any thoughts?

[Joey]

I believe I have gotten the same message before. I do not however, know how to fix it. I dont know. I would be interested in how to fix this though.

[HWM]

This happens when you call for a resource that doesn't exist... Par example: load.sound(1); when you don't have SOUND.001 imported in your VOL file...

[happyturk]

....yes.

That explains it exactly. I feel like an idiot. >_<;

Thank you. I'm glad it was something simple to fix, at least.