generally it is not sp_prepexec that is the root cause of 100% cpu usage, it is usually a very poorly formed query/design. sp_prepexec is used by ODBC and OLE to try an optimize sql that may or may not be used over and over again. So when the connection first issues free form sql, it will use prepare it as more or less a temp. stored procedure and then call it over and over as need, on that connection. It can be turned off.