How to change the "Recovery HD" partition to type "Apple_Boot"?

Both the laptop and the PC are USB hosts with female type A connectors. You cannot directly connect two USB hosts with a Male-Male cable. One of the device's would need to act as a peripheral, which wouldn't be supported by the USB chipset on the motherboard.

Some devices support acting as a host or peripheral with USB on-the-go, but I don't think any personal computers would support this.

There are active cables that act as two peripheral's (one for each host), but you would have to make sure they were supported by the OS.

There are ways to connect devices using USB, such as http://www.linux-usb.org/usbnet/. This however simulates an ethernet network, which you are probably trying to avoid. I'm pretty sure it's not possible to connect a computer as a USB drive.

Your best bet is probably the regular network way, or you can write the USB interconnect driver yourself.

The issue with using USB in this manner is that USB is a Master-Slave protocol, and most computers only come with Master or Host capable USB ports.

If you were to find a way to add a Slave (or Device) port to your laptop, then you could use the Mass Storage Gadget implementation found here to make your laptop show up as a mass storage device.

If you can't find a way to add a Slave port to your laptop, you can go with the Ethernet(or similar)-over-USB method using a host-to-host network cable; this requires a special USB bridge cable, not a straight USB A to A cable. If you use a straight USB A to A cable, you can burn up your power supplies! This will create a USB based network connection between the machines, one that you can even bridge to your Ethernet network. You'll also need the appropriate drivers for the cable for each system.