This happened to me today on an Acronis restored Small Business Server box (to different hardware using universal restore). The issue is that the HP server that the image came from had HP drivers that ended up blocking the broadcom drivers on the Dell...
A while back I posted about how Broadcom and it’s TOE system in the Dell PowerEdge 2900 stops ISA from functioning on Small Business Server 2003. Well, since then I have installed a few more Dell servers, all with Intel cards and have had no problems...