issue database tie sharepoint workflow integrated confidence options

good morning everyone,

i'm controlling an emanate controlling sharepoint workflow digest (c#,
vs 2008) joining database. here database tie
string:

data source=dbserver;initial catalog=dbname;integrated security=true; 

when i try run following formula i following blunder ...

sqlconnection dbengine = new sqlconnection(constants.dbconnection_string);
dbengine.open(); 

"login unsuccessful user 'domain\machine_name$'"

what i need pass by logged user's credentials.
i've got impersonation incited nonetheless doesn't seem flitting
through. any suggestions unequivocally many appreciated.

thank lay any advice,

scott vercuski