ok, so i got just a normal pc mic, worked fine on my old pc..but that broke..and now it wont work on my other pc, mic still works tho cos i tried it on my mates laptop. but this pc just wont pick up anything.its not muted or nothin like that..any ideas?

I assume you are using Microsoft's default drivers for the mic.
I am also assuming you are using Windows XP.
If my assumptions are wrong, let me know.

Connect the mic as usual and leave it connected.

Check your Device Manager.
Is there any device with a ? or a !
If there is, click on that device and delete it with the keyboard Delete key.
Is there an "Other" catagory?
If there is, delete any devices in it.
Look for the mic device. Delete it.

Reboot.

After rebooting, Microsoft should reload the correct drivers.

Let us know the results. If we are lucky, the mic will work now.

Good Luck