|If you're connecting to the internet through a SOHO Router (and you are) then the IP from your ISP should be configured on the external (WAN) side of the router.|
Chances are your client computers are getting their TCP/IP settings from the DHCP server in the router and are something like the following:
Check the IP's on your client computers. If I'm right, then know that changing one of them to one of the IP's from your ISP will actually cause it to stop communicating on the network.
There are two rules of computing one should learn to live by and they are:
1) KISS (keep it simple stupid)
2) If it ain't broke, don't fix it.
Believe me, I live by those rules........lol.........in your case, think #2
Unless there's some specific reason to apply a static, external IP to one of your PC's, don't bother. Especially if your present setup is working properly.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.