*Replying to Abbie*
Sorry about the delay, Abbie.
i use windows XP =P
Okay. It sounds like you've been using the following document:
[Removing and Reinstalling iTunes, QuickTime, and other software components for Windows XP|http://support.apple.com/kb/HT1925]
The silly sausages at Apple have forgotten to include explicit instructions on how to uninstall
BonJour in that document. So I think that's probably still installed, and so your mdnsResponder.exe process is still running, and so you get that message about mdnsNSP.dll when you try to delete the BonJour folder.
So, head into your Add or Remove Programs control panel again. Select "BonJour" and click "remove".
Are you able to delete the BonJour folder now?