Sorry to necromancy this but I am having this exact same problem on an XP64 rig I just built. I was wondering if anyone else had run into this problem since October and maybe had a fix. TCPIP works fine, and I can map drives TO the box, but I can't map out, and the Client for Microsoft Networks refuses to install. Also, the related services (workstation, server, computer browser, etc.) do not appear on the services list. I have an Intel DP965LT motherboard, using the built-in ethernet and drivers that Intel provides for XP64. I am using the latest drivers, and have tried removing and readding them but the result is the same. I have all the latest XP64 updates, and even threw on the SP2 RC from MS's site to try to get this working, but to no avail. This is not a unique problem, I found a handful of references to it on Google (including this post) but no real answers. One person claims to have fixed it by fiddling with their NIC drivers (NIC unknown brand) but no details are given.