I have been having a problem with the lost of sound to my PC for some time and not having any success trying to fix the problem. In part the problem is probably me as I haven't been able to understand the good advice that people have been giving me. Below is some advice that someone gave me a while ago. One of the last recommendations was to delete my sound device which is an AC97 something or another ( that's how hopeless I am ) which I have done. My Sound Problem posted in another forum I got an indicator that I had new hardware when I restarted the PC but still no sound. I did find however that there is a hissing coming from my speakers and when I adjusted the volume control the noise of the hiss got louder as I turned it up and down etc. I tried to play the Media Player and got this message from the Windows Media Player Error Centre : 0xC00D11BA: Cannot play the file Windows Media Player cannot play the file because there is a problem with your sound device, such as a sound card or sound controller. You may encounter this error message for one of the following reasons: Your sound device is in use by another program. Quit other programs that may be using your sound device, and then try to play the file again. Your sound device is not functioning properly. To troubleshoot the problem, see the Sound Troubleshooter in Windows Help or refer to your sound device's documentation. You do not have a sound device installed on your computer. Install a sound device, and then try to play the file again. Error ID = 0xC00D11BA, Condition ID = 0x00000000 How can I find out what this application is that is using the sound card? I'm at my wit's end. I can't work out what the problem could be and apart from some other problems I'm having with the PC, this is turning out to really annoy me. I apologise that this is a long post and I thank you for taking the time to read it. KR Hackbridge ps Just in case you need to know, I have Real Play, Quick Time, also installed. I have deleted Winamp which I recently had as I thought that might have been the problem.