I recently purchased a Dell inspiron 630M notebook with Windows XP home edition. When I first got it, the onboard microphone worked fine, I tested it by recording my voice using windows sound recorder. That worked fine.
The next time I tried doing it a few months, I could barely hear myself, when I tapped the actual microphone locations, only dull bumps could be registered. Now when I try to do the same, nothing is audible, nothing registers on the 'wave' screen in windows sound recorder. Similarly, I can't record anything from line in.
I know I have done something. Yes I have checked the microphone volume and yes its fine - done that about 50 times. When I 'test' the hardware using the 'sounds and audio devices' properties dialog box accessible from control panel, the process indicates that it has failed.
In past months I have hooked up various micropones to the external microphone input and tried them, and they were really faint. I even used an amplifier to increase the volume, and whilst it could be heard, there was heaps of noise, sounded awful.
A couple of times I plugged in my speakers into that external microphone input socket by mistake, but I can't imagine this would do anything.
I uninstalled the only device in my device manager that appears to be my sound card - 'SigmaTel high definition audio codec' under 'Sound, video and game controllers' and then rebooted to automatically reinstall it. No improvement.
I tried going into setup when I start up and seeing if there is any settings in there that might be worth changing, can't see anything.
The annoying this is that this happened with my last dell laptop :(
If you can provide a solution to this problem, you are a genius.