Quote Originally Posted by R'as al Ghul
Isn't it enough to enable "Internet Connection Sharing" for the network connection that your desktop PC uses to connect to the Internet?
Have you tried that?
The network setup wizard did that automatically at the start, and I've checked it since.

On the desktop's internet connection's Advanced tab, I have all 3 options checked under Internet Connection Sharing, plus the Internet Connection Firewall.

On the desktop's LAN connection's TCP/IP tab, I have:
IP address: 192.168.0.1
Subnet mask: 255.255.255.0
Default gateway:

Preferred DNS server: a.a.a.a
Alternate DNS server: b.b.b.b

Where a and b are the DNS addresses used by the internet connection. I've resetted first the laptop, then the desktop, but the same error persists when I try to look outside on the laptop: DNS not found. File sharing works, but the laptop can't access the outside world.