Hi all, I have a solution with three projects. The first is a Winforms project which displays data in the usual way via textboxes and other controls. The second is my DAL which is very basic and takes care of connecting to my database and returning datasets. The third is a WCF service which can also access my DAL. This whole scenario is setup as a testbed for future projects. I have the Winform app setup so I can switch between using the WCF service or as a straight call to my DAL methods. Also in the mix is the option to use a SQLConnection or ODBCConnection - all this (amazingly) works very well using the non WCF scenario. When using the WCF way it all works fine except when I switch to using ODBC where I get an error "(IM002) [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified" ?, the WCF service is hosted on the same machine ( IIS ) and accesses the database using SQLConnection without error but can't find the ODBC driver for some reason. Both SQLConnection and OdbcConnection use a connection string stored in a config file, I've tried hard coding the connection string in case there's a problem reading the config file but it doesn't help. Any help much appreciated.