Is it possible to connect my laptop to my desktop in a way that it can identify one of its internal HDD's and write data to it? A USB connection would be preferable.
In short no, however you could possibly write your own program to do it.
Why don't you just put your desktop on a home-group and then just connect to it from your laptop to transfer data?
yes and no. not that i know in usb form.
what im doing at home:
i have a desktop, laptop and a server
my server harddrive is shared on my local network
both my laptop and desktop can write/read date to/from that disk.
so if you share your desktop's hardrive in your lokal network, you can write data to that drive.
hope this helps