help me!

[labluekatt1721]

hi  i am new to this podpost
and i just downlaoded Audacity and the lame codoe  thing 
and i have my head phones and my  old mic and its all installed
 and set up but it wont let me choose an input sourse 
i have a windows vista and i havent a cule what i did wrong 
i downlaoded Audacity before back in 2003 and i just set it up and it work fine 
but now for some reason the new one that i just downlaeoded today wont 
let me choose a input sourse can some one please save me from the stipedness
of my own brian... please!