I searched for ppp on win32 and on cygwin, without result. Tried compiling pppd from source on cygwin, but it's too specific to the OS.
I thought of something different : use ssh to connect over the usb link and use ssh's internal port-forwarding. On the empeg sshd should be running and a proxy for routing the usb to the ssh-port. The ssh client has got a proxy option which lets it execute a program to setup the connection; another small proxy for win32 should be written.

Frank van Gestel