This isn't the first time this has happened and usually I just reboot the computer and the sound is back. This time I went to device manager and found:
Microsoft Kernel Wave Audio Mixer
Cannot load the device driver. May be corrupted or missing. Code 39.
driver is kmixer.sys

I can reboot and this will clear itself up, but has anyone else had this problem and what did they do to fix it??

Thanks for any replies.

Looks like PnP is not quite working, it found a Mixer driver but it turns out to be the wrong one. You need to download the correct sound drivers and reinstall them or select a driver manually (point it to \windows\inf or wherever you put your sounds drivers eg CD).

I don't know if this will fix your particular issue, but I just started getting the message about "new hardware detected" and that I needed to allow windows to find the driver for my "Microsoft Kernel Audio Mixer". And it responded each time with the warning about it not having passed "Windows Logo Testing". If I told it to cancel, guess what - no sound whatsoever. I've been running SP2 all along and had done nothing to make this happen, however I've recently gotten similar messages for a new jump drive and a second hard drive I just added. Decided to go to Windows Update site, and although I've had the computer set for automatic updates (and it still appeared to be) I couldn't get updates because of the following (copied from their page at

http://www.update.microsoft.com/windowsupdate/v6/default.aspx?ln=en-us )

as follows:

The site cannot continue because one or more of these Windows services is not running:

• Automatic Updates (allows the site to find, download and install high-priority updates for your computer)

• Background Intelligent Transfer Service (BITS) (helps updates download more quickly and without problems if the download process is interrupted)

• Event Log (keeps a record of updating activities to help with troubleshooting, if needed)

To make sure these services are running:

1. Click Start, and then click Run.

2. Type services.msc and then click OK.

3. In the list of services, double-click on Automatic Updates and then click Properties.

4. In the Startup type list, select Automatic and click Apply.

5. Verify that the Service status is started, if the Service Status is Stopped click on the Start Button.

6. In the list of services, double-click on Background Intelligent Transfer Service (BITS) and then click Properties.

7. In the Startup type list, select Manual and click Apply.

8. Verify that the Service status is started, If the Service Status is Stopped click on the Start Button.

9. In the list of services, double-click on Event Log and then click Properties.

10. In the Startup type list, select Automatic and click Apply.

11. Verify that the Service status is started, If the Service Status is Stopped click on the Start Button.

I followed the instructions and in fact two of three were disabled; afterward I downloaded 12 updates and rebooted; problem appears to be solved as it booted with sound and didn't "find" any new "hardware".

Hope it works for you.

i used registry mechanic and it seems to have worked maybe give that a try or anything that is a registry programs that fixes errors or something. i have a key for 7.0.0.1010 if you need it

Thread closed.

Giving out keys for software is not acceptable here.