Certainly: Virtually every DSL modem with a built-in router can have the internal router disabled by setting it to "bridged mode" -- in short, all of the modem/router's smarts are disabled, raw ADSL signal goes in one end, and a single raw ethernet connection comes out the other.
There's several people here with Express boxes hooked up to an otherwise-smart modem-router combo that's had an electronic lobotomy
