Problems with setting up Mic - Logic Express

[Sunkjunk]

Hello all...

I'm a newbie so massive apologies if this has been covered countless times before but this issue is driving me to insanity...!

I've written a few tunes in Logic Express and wanted to add vocals, but am having problems getting the software to use my external mic. The mic is registering in the main system preferences but when it comes to logic, nothing. I tried running the set up assistant again and it notices the mic - I add it as the main input but when the assistant finishes running it says it's unable to use the mic and reverts to using the built in audio (ie no mic).

I'm using a G4 PowerMac. It has two USB ports - I use the first for the keyboard and the second for the mic.

Can anyone help?