Home Network Problem

Trying to solve a problem on a friends PC where she said she could not connect to the internet (DSL)
I added her PC to my home network, added a working NIC and cabling. The PC is unable to reach the gateway, but is able ping loopback and other pcs on the network if i assign it a static IP within the same subnet. The router does have enough addresses available in its scope for this pc.

All of my networked PCs connect to a router which is connected to the DSL modem. All other PCs have no problems connecting.

The ISPs diagnosis is a virus, but updated virus scan and malware/spyware scans show nothing.

Any insight would be greatly appreciated.