Recently some of the hosts that I monitor and provide server administration support upgraded their MSSQL 2000 to MSSQL 2005. The problem started when we tried to add MSSQL 2005 database service to monitoring. Nagios would simply not check “MSSQL$SQLEXPRESS” and return a Unknown state. Obviously the $ in the middle of the service name was causing the issue. Found out later that we need to use either two $$ or quote the dollar sign so that it shows MSSQL$”$”SQLEXPRESS.