I'm honestly thinking your best bet would be to buy some sort of switch/router.
You plug the switch/router into your Cable Modem and then run Ethernet cables from the switch/router to the PC and (as necesary) the netbook.
This will enable you to just connect devices to the switch/router at will, changing which you're using to access the Internet or whatever, without having to power cycle everything.
My recommendation would be something like this:
http://www.amazon.co.uk/Linksys-BEFS...2361116&sr=8-4
Not necesarily bought from Amazon, and not necessarily for that price.
You should be able to just put that in place of your existing connection to the PC (following the same swap-over procedure as above) and then connect Ethernet cables to any devices that you fancy.
That one doesn't have wireless, but if you wanted wireless you could get a wireless router and accomplish the same thing.