I would switch the cat5 cables around on the router. That is connect the pc that works to the port the pc that doesn't work is connected to and vise versa to verify the router you have is actually bad.
Wireless is nice but you may get more headaches with it. You will need to upgrade the nic's in your pc's to wireless, get them installed and working. Then you may have a problem with signal strength etc. Everything may just work... but you know how this stuff goes