Thread bumped for Arkell.

Windows XP Firewall :

Start|Control Panel|Security Centre

Under "Manage Security Settings for:"
click on Windows Firewall.

click on Second tab "Exceptions"

click on "Add Program"

Scroll Down list to relevant version of mtw.exe
(if you have dual installations, both icons will show and the VI version has the triangular-shaped icon)

Click Ok.

Exit out of security centre, connect to internet and fire up the game.

If there are any problems, you'll have noticed the button "Add ports" next to "Add programs". See the list of required ports further back in this thread.

Read the online help for the appropriate syntax for entering lists of single port numbers or ranges of port numbers.
The prompt has a radio button for TCP/UDP, so you may need to enter every port number twice over, once for TCP and again for UDP.

When done, Tick the relevant tickboxes on the Exceptions list for the items you've added.

I have Windows firewall disabled at the moment, so this is incidental, but I only have "Microsoft Direct Play8 Server" and MSN Messenger 6.2 ticked. The other items in the default have specialist uses and are best left closed unless you have a genuine purpose for them. Some are popular points to be 'probed' by hacking attacks.

Hope that helps.