You are almost certainly going to have to use manual port forwarding to get all 4 computers working. In your situation, you might strongly consider purchasing some IP cameras. You could easily monitor 3-4 IP cameras and a built-in USB camera by using only one laptop (assuming it has decent processing power--aka probably not a netbook). I use the LOFTEK CXS-2200 and love it...good picture, pan/tilt, and audio (all features supported in iCam)...and it's only about $70/camera. The downside of this camera is that it's a pain to setup the first time. I'd also recommend that you wire the IP cameras if you go that route...and reduce the frames per second from 30 to 5 or so (it'll reduce your energy and processor usage).
If you're committed to using 4 laptops (which will use much more electricity than the alternative setup I described), these are the basic steps you'll have to follow:
1) Configure manual port forwarding in icamsource on each computer, using a range of 6 UDP ports per camera/computer...with none of the ranges overlapping. Ex: Computer 1: 12000-12005; Computer 2: 12006-12011; etc. There is a .reg file linked on the forum that will allow you to make the manual port forwarding feature visible on Windows computers.
2) Assign each computer a static IP address on your local network. The first 3 set of number in the IP address should be the same as the IP address of your router. The final set of numbers should be between 1-254, and should not match each other or any other device on your network.
3) In your router, configure port forwarding for each computer, using the appropriate IP address and range of UDP ports for each computer.
4) Reboot everything (including the router) just to make sure all changes have taken effect.
