I'm currently in the process of setting up all of our new servers in a Win 2003 Active Directory Domain.
Currently working on getting all of the servers set up for backups. Noticed during this that I could not see most of the new servers in the "browse list" in Windows Explorer.
After doing some poking around found Knowledge Base Article 231312 on Microsoft's web site. Basically it says that a system's description (usually set up through the Computer Name tab in System Properties, but can also be set up through "net config server /srvcomment:"commenttext"" from command prompt) cannot be longer than 48 characters, or the system will not show up on the browse list.
So I checked and lo and behold, that was exactly the issue that I was having. Problem solved and lesson learned.
BTW as I go through my AD migration and Exchange 2003 migration I will be posting more tidbits like this, so stay tuned.