Copiado de Compartilhando a Internet do laptop para a área de trabalho através do cabo Ethernet? :
If your laptop has Internet access from wireless, you can use Internet Connection Sharing on the laptop network adapter to share with the desktop.
- open the network control panel
- change adapter settings
- right click on the network adapter
- select properties
- the Sharing tab
- and then check the box to allow sharing
You can also bridge the two adapters on the laptop to share, although to do that ICS must not be checked.
This also assumes that at least one of the Ethernet adapters is gigabit capable, and thus has auto-MDIX, so you don't need a crossover cable.