I had this problem for bloody weeks.
The answer might be to re-install under admin rights...
It might be lots of things.
But befor you test all theese options i would highley reccomand plugging in your mic... Easyest fix...
I had this problem for so long.. I just plugged in my mic and it bloody worked.
I have no idea why this works.. But it does.
It took me like 2 weeks to find the solution, it was one guy just saying plug in your mic.
Three words to a 2 week problem.http://www.sevenforums.com/gaming/24080-call-duty-2-library-not-registered.html