My microphone line-in jack isn't working.

Question

I want to use an external microphone for online gaming conversations. I have a headset with both mic and earphones. I can hook the earphone jack up and can hear fine, however when i hook the microphone jack i can't get it to work.
Yes, i have gone into system preferences/sound/input and selected the line-in tab. Nothing is letting me use an external mic. (although the internal mic works fine)
The funny thing is, when i boot into Windows XP, i can use the headset perfectly fine, both microphone and headphones.
What's the deal?
iMac C2D 20" 2.33ghz, 1gb, 256vram   Mac OS X (10.4.8)  

Answer 1

RebelToRumble
I found some information on Apples Web site that may shed some light on this subject. The link below has more info.
The last line may indicate the problem, also I found somewhere some mic's need their own power source. Look around on the Apple site it gives that information also.
http://docs.info.apple.com/article.html?artnum=43019
To turn on the microphone and use it as the sound input device, follow these steps:
1. From the Apple menu, open the Monitors & Sound control panel.
2. Click the Sound button.
3. From the Sound Monitoring Source pop-up menu, choose Built-in Mic or External Mic.
4. Click the close box to close the control panel.
Sound input port
Important: Some microphones will not work properly without the use of a third-party sound recording application.
Smoky