Running two network cards will work, then you have to bridge the networks together so computers on the other network can access the ADSL network.
File sharing will work on a dynamic setup, but the computers should be on the same workgroup. If they're not, you most likely won't see the shared files.
As your setup is now, set the computers to dynamic, then run the network wizard on each, selecting the appropriate options for the internet connection, workgroup, and file sharing. Windows should then set everything up for you.
Like I said before, this is how mine is setup and it's how I set networks for other people and it works fine.
Microsoft's 'How To' for bridging connections:
http://www.microsoft.com/windowsxp/using/networking/expert/crawford_02april22.mspx