Gladly, and welcome to the forums. Please keep us posted as to what is happening in regards to both computers, when you change things around.
You will probably need to reboot the whole network, when you do so shut the computers down, the router down and the ISP provided device down.
Make the changes and then bring them up in reverse order. ISP provided device, wait till all lights are green and steady, then router, again wait till all lights are stable, then primary computer, see if you can establish an internet connection, then secondary computer, see if you can establish an internet connection. Then see what they both have for an IP addressing scheme by typing ipconfig /all into a command prompt on both and comparing. If they seem to be in the same subnet with an actual IP address of say maybe one off, then make sure you can ping one from the other by that IP address.
And let us know.
Regards (nice turtle, I think)
Randy