OK - back to basics and yr post #5
LAPTOP
Let's assume Windows XP? You have not said. However, you need to get to Start/Run and type cmd in the box and enter. After the > in the black screen (you should then get) type the following ipconfig /all (*NB space before /all)
Look for 'ethernet' or 'RJ45' or something in the text that comes back and tell us what the 'IP address' (6th line down) is and also 'default gateway'. These are what your laptop and router are using. Can you also say if DHCP and autoconfig are enabled?
You have not mentioned the desktop before. Does that work with the router?
If not, do the same again on that and post back.
"I had to reset values from another connection and reboot both to get back up and running." - what does that mean you actually did?