Is there a way to make a pc look like a USB drive to a device that reads content from a USB drive?
Solution 1:
What you need is something similar to a USB data copy cable. The problem is that data copy cables just use custom software on both ends to manage the copy - they don't actually make anything look like a drive. You need custom software on the PC end, and then enough brains in the middle to pretend to be a USB drive.
If you were up to reverse-engineering one of those copy cables, you might be able to use it as the basis for what you want, but you'd have to write all of the software yourself.