All sorts of things could be wrong here, but I suspect maybe DHCP has been turned off and static IPs set? Although the computer shop situation seems a bit wierd.

Connect ethernet to router and run "ipconfig /all" from a command prompt and paste here?

Possibly you have some different to normal IP settings at home (most would use 192.168.1.0/24 on their home network with 192.168.1.1 being the gateway and DNS server).