You could try this:-
On the PC that is already connected:- Log on
Click Start, and then click Control Panel.
Click Network and Internet Connections.
Click Network Connections.
Right-click the connection that you use to connect to the Internet.
Click the Advanced tab.
Under Internet Connection Sharing make sure that the box Allow other network users to connect through this computer's Internet connection is unticked.
On the second PC connect the ethernet cable
From the Start menu, click Control Panel.
Double-click Network Connections.
Right-click the Local Area Connection icon, and then choose Properties.
On the General tab, highlight Internet Protocol (TCP/IP), and then click Properties.
Choose Obtain an IP address automatically and Obtain a DNS server address automatically.
Switch both PC's off and see if this works
You then need to go into the Sky Router Admin Pages
Type 192.168.0.1 into the URL bar towards the top of the page (not into Google) This should then take you onto your Router page
It will ask for User name and Password
If you have not changed these they should be Admin and Admin or Admin and Password.
Go to LAN IP Set up and make sure that Use Router as DHCP server is ticked
Switch off both PC's and try again.
Hope you can follow these instructions.