Remote access to airport disk from Windows

I would like to access my Airport Disk from my Airport Extreme (802.11n) over the internet; not just from my network, but from any pc in the country (similar to ftp). Please help me with the Airport Extreme settings that will enable me to access my Airport Disk from any Windows based computer, from anywhere over the internet.

I've read several discussions which either describe how to access the Airport Disk on your home network or how to access you disk over the internet on a Mac. This is not what I'm looking for. Again, I want to access my disk over the internet from any PC.

Any assistance would be greatly appreciated.