audio hookup from PC to Receiver

Helping a friend who has multiple speakers though out his home driven by Kenwood receiver.  Using a Y cord with  stereo  jack into PC  and 2 RCA jacks into rcvr. to play music stored in his PC. He also wants to be able to the use the  5.1 PC speakers too. Problem is: when they're connected, the gain on the rcvr drops considerably. The PC is a Dell with 6 jacks.  Can this be corrected? Thanks.