The reason you are seeing this is becasue you have set Client For Micosoft networks to log on to an NT Domain. This is a system setting in Windows.
To fix this please follow below.
Goto control pannel.
Double click on the network icon.
Double click on the entry for Client For Microsoft Networks.
Here you will see a check box for "Log on to Windows NT domain", untick this and restart your computer.
If you need any further info please let me know.
"Networking is no longer a black art!!"