"Connect to computer" User name disabled !

Hi All,
My system running in Windows XP is connected to the
intranet as workgroup. When I try to access my machine
from another machine also running Windows XP, the User
name combo box alone is disabled! The default entry in
the username is as XPBAKUPPC\Guest. My computer name is
XPBAKUPPC. I have renamed the in-built Guest account for
security reasons. Now I am not able to log in to the
XPBackupPC at all from another XP machine.
Any help or suggestion would be useful,
Advance Thanks,
Tajab