Deployed In Afghanistan With Bad HDD?

I am currently deployed in Afghanistan with the US Army. My internal hard drive crashed last week. As one can suspect, it is rather hard to get parts out here. I have a 1TB HDD that is actually a SATA internal for a desk top, but I have a dock that allows me to use it with any computer with a USB... basically an external (at this point). I have my recovery disks. I've been told there is a way to make windows 7 install to that "external" but had had no luck on finding information or instructions on how to do that. I have no working internal hard drive, my bios is good, it is set to boot external device, internal optical