I'm not sure which Windows laptop you're referring to, but as far as I know, you cannot use the displays of laptops as external monitors. The VGA/DVI/mini-DVI connectors on laptops are all for video OUT, not IN.
Connecting two laptops via an ethernet connection will not give you the ability to use one as an external monitor, except if you use a screen sharing program, which still only gives you the option of mirroring your primary screen.
Finally, those adapters you see on Apple's website are for the video OUT ports on the laptop. So they will do you no good in trying to use a Mac laptop's screen as an external monitor.
So to summarize, there's really no way to use a Mac laptop's screen as an external monitor unless you rip it off and interface with the ribbon cable directly.