Hi Everyone, I have tdi based client which works fine in win2000 and winxp but in vista it fails at TDI_CONNECT. It is able to open a transport and connection endpoint and associate the two. But when it goes to call TDI_CONNECT it fails and return STATUS_ACCESS_DENIED ( 0xC0000022 ). I have even disabled the UAC ( User Account Control ). I also tried the tdiclient from http://home.mindspring.com/~antognini/drivers/ which also fails to connect with the same error code. It would be real helpful if someone could help me resolve this problem. Thanx Amit Chopra.