Problem with connection string

I have a problem with the connection string.....i can't connect to my database
I'm using sql server 2012 on a windows 7 and i tried and tried and tried to
connect to my database unfortunately its not working .... it keeps actually giving me this error

ADODB.Connection error '800a0e7a'

Provider cannot be found. It may not be properly installed.

Its says on this line where i have the problem Line 68

set dbconn = Server.CreateObject("ADODB.Connection")
dbconn.ConnectionString = strConn
dbconn.Open (this line where the problem is)


So the connection string that im actually using is this :

strConn = "Provider=SQLNCLI;Server=SAM;Database=Marketing;Trusted_Connection=yes;"

can someone help me pleaseeeeeeeeeeeeeeeeeee ???

PS: im using windows Authentication not sql server authentication is that the problem ?