My microphone does not work on my pc

Hello, i'm using windows 7 32bits, before a couple of months i was using XP and my mic. workd as well but now with the win. 7 it does not!! when i go Comtrol Panel> Sound> Recording .. I find that there is not a back panel jack, that means that i can't use my recording device. But, i can hear every sound as good as it should and don't have any problems with the sound here!
* The same mic. works excelent on other pc's and i've tried it on another 2 pc's such as Apple macbook pro and Acer laptop.
Can some 1 help me plz ??