To Do This You Will Need:
1: A Computer With A Lan And Dialup Adapter
2: Windows XP or Later
3: A Ethernet Router
4: 2 Ethernet Cable's(Only One Needed If Router Supports WiFi)
Step 1: Setup ICS(Internet Connection Sharing) on the computer with dialup.
1:Open Up A Windows Explorer Window and Enter
Control Panel\All Control Panel Items\Network and Sharing Center in the address bar and hit enter
2: On the left side of the window click: Change Adapter Settings.
3: Right Click Your Dial-up connection And Click Properties
4: Click Sharing
5: Enable: Allow other network users to connect through this computer's internet connection
6: Click OK