Opening a Quark file that has been created in Quark 8.5 (on a Mac) on a PC using Quark 7?

Hi

I keep sending a colleague a Quark file created in Version 8.5 on my Mac. But they can't open it in Quark 7 on their PC.

Is this a Quark Version problem or a Mac/PC problem?

They say they can't see the extension... is this the issue? I have tried adding an extension .qxd and send it, but to no avail.

Second question... Has anyone experienced any issues when transferring Quark files using DropBox. When I have done this... from my office Mac to home Mac, the file won't open in Quark.