1. Go to Start >> Control Panel >> Network and Internet Connections >>
Network Connections.
2. Right-click the 'Wireless Network Connection', then click
'Properties'.
3. Click the 'Wireless Networks' tab.
4. Double-click on the name of your wireless network, under 'Preferred
networks'.
5. Compare the settings on each tab (Association, Authentication,
Connection) of the computer that works to the settings on the computers
that are not working.
6. Change the settings on the computers that are not working to match
exactly those on the working computer.
Note: All computers should have exactly the same settings. If you
change settings on the router, you will need to make those same changes
on all computers that connect to that router.
You can follow this tutorial
http://www.leeindy.com/how_to_stay_connected_to_a_preferred_wireless_network.shtml
up to step 10, which shows the Connection tab.