If you want to do it on windows, you can add a static route to each of your interfaces.
You'll have to add static routes to the IP Networks at each NIC from command prompt (or make a batch file to use only when required) :
route add destination-address mask subnet-mask gateway-ip
Example: let me assume that the ip address at the interface on A towards B is 184.108.40.206, and that towards C is 10.1.1.21
route add 10.1.1.0 mask 255.255.255.0 10.1.1.21
route add 220.127.116.11 mask 255.255.255.0 18.104.22.168
Or if you want to 'simulate' a router on your PC, use GNS3. Check this out:
Place a router and connect two clouds to two of the router's interfaces. At the cloud configuration, assign each cloud an NIC from your PC. So now you have one cloud connected to each of the PCs NIC cards. Assign IP addresses on router and clouds. This basically results in both networks at your PC's NICs being connected to your router in GNS3.