How to save post file to local disk?

Hi,

Dose anyone know to implement this:

I have a post form include a file and pair of radio buttons (let user choose file saving location). If user select “save to remote”, the file need to be upload to remote server, when the user select “save to local” the file need to be saved into default hard drive in local network. No problem for me to implement upload file to remote server, how can I save this post file into local disk? I know PHP only execute in server side. Have any client side languages not rely on Microsoft technology can do this?

Any ideas or hints?

Thanks

Richard