Have a situation with an office using 3 computers (all XP) and using a router to connect them to the Internet. However the Router conflicts with the SpeedStream DSL modem.
If a single computer connects with the DSL it works fine; through the modem none will work.

Does each computer have to have a static IP to connect through the ROuter or is there a simpler step?

Need help ASAP!!!

Have you run the Network Setup Wizard?  If not, run it (it is located in the Network Connections in the Control Panel)

When you run it, I think that your situation you would want "This computer connects to the Internet Directly or through a network Hub..."

See pic