what is the cheapest approach to do this?
Answers:
If you want both PC to be on at alike time later you involve a Router. If with the sole purpose one desires to be on after move your Broadband Modem to the other PC when needed or receive a second B\Band modem. You can not run 2 B\Band modems at matching time on alike queue.
If you desire on a Router afterwards it go where on earth the Modem is in a minute. Then connect the other PC via a Cat cable or turn Wireless. Your looking at give or take a few lb50 ish for a Router and Wirelss card, Cable instead of Wireless card simply a couple of pounds smaller quantity.
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Get a wireless router and a wireless card.
if they are both desktop notebook's afterwards you can buy an ethernet cable and join your computers together by introduce yourself sharing. if you capture another usb modem for the other computer later individual 1 laptop can be online at duplicate time