xml web page directly to a saved fike on disk

I have an xml file being brought back to my Web app as an html page.. Thing is I don't want it as a page but saved to a file on the server disk.......
The request is made by:
Html://www.somesite.net/getfile?filename

This opens a New Web page showing my xml information.. Thing is I don't want it as a page but saved directly to a predetermined location on my server so I can process it... How how how ????

Gollnick