Unfortunately, due to the nature of W32.Downadup [Symantec] ( AKA Win32/Conficker.A [Computer Associates], W32/Downadup.A [F-Secure], Conficker.A [Panda Software] ), you pretty much will have to kill your network and return it to a LKG state, or start from a clean slate. This worm has likely infiltrated every Winbloze box you have. 
There is not much way to remove it and maintain a functioning system and since a rootkit may likely have been installed by this self propagating bastard, you can't trust anything you see. 
Format and reinstall. Format and reinstall. You'll be doing this for a while.
And in case you still have a compromised system on the network or there is some other means exist for your system to be touched again, then you will want to download all the Updates for offline install.
Good luck  ,
MITH

I agree. Try to disinfect before you toast your computers. If you cannot you may have no other choice.