I have a Sound Blaster 5.1 VX audio card. The card has one 3.5 jack for audio ingress that is used both for mic in and line in. I need to use it as mic in but I can't find a way to tell the audio card that I need it as mic. Now it is working as line in and the incoming audio is very very low on volume. On windows recording device panel both mic and line in are presents, but only line in has the volume bar, instead the mic is is stated as "currently unavailable". I have Windows 7 and the latest drivers.
So this is basically a "FlexiJack" Issue. The setting for flexijack can be configured through the creative sound blaster control panel. Under the Flexijack tab, there is a setting to make it either a line-in or a microphone.
The worst thing about this setting is that line-in appears to be default, so any poor soul looking for MicBoost (which is now missing) for their Mic will get completely confused and be looking in the wrong place.
When Flexijack is set to line-in the volume on your microphone will be extremely low to the point where its useless. Once you set it to Microphone everything starts working the way you expect it too. Including your question about the mic, the line-in will disappear and the Mic will be available.