Assuming all ur connections are made. back/rear panel for speakers. front panel for headphones. Go to your audio manager. (bottom right of the screen an icon of e.g. realtek audio manager) double click that. Click on audio i/o tab. On the right side you'll see ANALOG tab, click on connector setting of this tab (a small spanner shape icon there) put on ur headphones and check/uncheck the menu options that you can see after you click on the connector setting.
This worked for me. Hope it works for you too.