I've never tried it, but I believe it is possible.
It's less to do with the SDK on your windows box (of which there are many variants), and more to do with the (closed) firmware on the drone.
Drones are controlled by sending commands over a standrd UDP port.
By default, the AR Drone acts a Wifi HotSpot and DHCP server, assigning your PC an IP address when it connects. Meaning your PC would need 4 network cards to connect to 4 drones.
But if you read the Developers Guide PDF, section 8.6 Network configuration mentions:
Mode of the Wi-Fi network. Possible values are:
- 0 - The drone is the access point of the network
- 1 - The drone creates (or join) the network in Ad-Hoc mode
- 2 - The drone tries to join the network as a station
So if you can get all 4 drones to connect to the same network, you should be able to send UDP packets to individual drones; and only need the one network card!