Webcam mic permanently on, causing feedback

I have a Microsoft LifeCam 5000 which I use for Skype calls. The microphone has recently become stuck ON so that all room noises are picked up and played through the speakers, even when Skype is not running (it's not set to open at Startup and I always quit when I've finished using it). Lifecam was in Startup so I disabled that but still have the problem; I checked it hadn't re-inserted itself in Startup - it hasn't.
The change may have occurred after I opened the LifeCam's own application to check lighting for the video image. I'm sure there's a simple solution (i.e. so the camera mic is turned off when the device is not in use) that does not involve uninstalling/re-installing - I want to be able to fix this if/when it happens again. In fact I think this problem has happened before, some years ago, probably when I was still running XP, but I can't remember the fix. Help appreciated.
I am running Win7 Home Premium with IDT audio.

Get into device manager; select and expand sound video and game controllers; then highlight your webcam mic and right click on it, then select disable...I have a logitech webcam with built in mic and had the same problem. This worked for me.

Thanks Bassfisher,
That fixes the problem BUT the mic is now disabled when I do want it i.e. when I want to use Skype. It looks like I can reverse the fix by repeating the process to ENABLE the camera mic. However I have to restart the computer each time I make hardware changes so this is not a great solution for me. Do you use the camera sometimes?
Happy Christmas,
Nick

For me, I use a headset with mic when I use Skype. I just change the settings accordingly in the Skype options. This way I have use of my webcam using Skype with out the mic and use the mic from the headset. I have my mic turned off in device manger and with the settings in Skype set to use the mic from headset as default and video source set to Logitech webcam as default. Works great for me.

I use Skype for video calls to my son and grandson in Australia, joined here by my wife and sometimes my daughter. Headsets wouldn't be the same.The webcam microphone used to work only when needed, so something has changed. If necessary I will try uninstall/re-install but don't know whether that will work either and would prefer a solution I can more easily repeat if there's a recurrence of the problem.
Any more ideas anyone?

That's great, thanks.
I'll use that procedure from now on. The only slight negative is explaining to my wife what to do if she wants to use Skype when I'm not there (not that often); she hates any complexity and won't remember - I'll have to pin the instructions on the wall! I still wonder what caused the change but at least I have a practical work around now.

Have you tried changing USB ports. It can cause the drivers to refresh and has been known to resolve awkward issues of this type, especially in Win7 systems...

Thanks Qdos, that's fixed it without me (or worse, my wife) having to mute it each time. Thanks to Riviversoft and Bassfisher also for their suggestions which did help in the meantime.
One slight concern is what happens if this repeats and I run out of USB ports. Can they be reset? Probably I'll just move devices around and I'll be OK for the lifetime of this computer.