Machines listed in the Microsoft Windows Network portion of the Browser (basically equivalent to My Network Places or Network Neighborhood), including Servers, Workstations, & Computers listed under any Domain Controllers, are not directly contacted by DNTU in order to update their icons. This is because there should already be enough information (i.e. O/S Flags, etc.) available directly within Microsoft’s Windows Network Browser itself (as part of your operating system). So the icons & tool tips for machines listed in this area of DNTU, as well as which category they are placed into (i.e. Servers or Workstations), will only reflect what information is available directly within Microsoft’s Windows Network Browser, which is part of your Operating System itself. DNTU retrieves this information by asking your local machine for it’s Microsoft Windows Network Browser, and then displays the information according to what’s returned by the O/S. DNTU does not modify this information in any way.
With regard to Computers, the list of Computers will give you a list of all Domain Members directly from the SAM (Security Account Manager) database within the Operating System. This could however list a lot of machines that are not currently online and potentially non-existing machines as well (if these computer accounts were not maintained/purged properly). All Windows NT/2000/XP/2003/Vista/2008/Windows7 machines must have a computer account in the Domain before that machine will be allowed to Login to the Domain. However, if you disjoin that machine from the Domain, or you rename that machine, or you move that machine to another Domain, or you decide to retire that machine, this account is never deleted until you manually cleanup this old information from your Domain. So that account will basically show forever until you manually delete it. Therefore, if this information is not being displayed properly, then it must be related to something within your network implementation & configuration. Unfortunately, we have absolutely no control over this behavior.
However, if these machines were listed under Active Directory, or under the Favorite Machines section of DNTU, then DNTU will attempt to directly contact these machines to update their icons. DNTU just basically request a NULL connection to the remote machine, and then asks the O/S to execute standard Microsoft Windows Network management API calls to retrieve the necessary information from the remote machine. The Microsoft Windows API call that DNTU uses to contact these remote machines is called NetServerGetInfo. Once a machine has been contact, then icon will change accordingly, and you will also be able to look at the tool tips to determine how the remote machine responded.
Red (or Blue with the Red "Prohibited" sign) means the remote
machine has not been contacted yet, or could not be contacted via
the Operating System's installed protocols, basically File &
Printer Sharing (i.e. 137-139/445).
Blue basically means the remote machine was contacted, and it also replied back that it was running Windows NT4, or Windows 2000.
Green basically means the remote machine is running Terminal Services (Windows XP & Server 2003 are included due to Terminal Services being part of the O/S).
However, if you feel your icons are not being displayed properly, then you may also want to check DNTU's Information pane for any errors encountered when contacting these remote machines (i.e. most likely System Error: 53 - Network Path not found").