Hi,
Can you please post with your operating system (such as Windows Vista, Windows 8, etc.)
In general, check to see if there are any updates from Microsoft:
In Windows 7, click the Start button, and type Device Manager into the Search field, or, if using Windows 8, press the Windows logo key + X, and then select Device Manager from the list. In Device Manager, click on the little triangle next to Sound, video and game contollers. Double click on the driver. On the driver's properties page, click the Driver tab. Click the Update Driver button. Click the "Search automatically for updated driver software" option. If prompted, install the latest drivers.
If you're still experiencing problems, it may be worthwhile to roll back the driver: Click the Start button, and type Device Manager into the Search field, In Device Manager, click on the little triangle next to Sound, video and game contollers. Double click on the driver (on my computer, it's IDT High Definition Audio CODEC.) On the driver's properties page, click the Driver tab. Click the Roll Back Driver button. If you're still experiencing problems, reinstall the latest updates by following the steps in the first paragraph.
I know it seems like I'm telling you to go in circles, but when I rolled back the drivers on my Windows 8 TouchSmart, my speakers and headphones started playing at the same time. My co-workers didn't want to have to listen to my music, so I reinstalled the drivers and that resolved the problem.