I mistook, I was going to write .lng are not scaned.
As I see there are 2 folders winamp puting temps to (and maby there are even more I don't know):
C:\Users\diman\AppData\Local\Temp
C:\Users\diman\AppData\Roaming\Winamp
Attached winampa.lng renamed to winamp.txt because forum doesn't allow lng attachments.
winampa.txt
Now I cheked dll's file names and it seems I was wrong, in the temp I see only *.lng instaled by Winamp(I Check it by ClamAV's history). And you say that dlls aren't scaned by ClamAV.
No Avast, Norton, AVG don't affect winamp. But ClamAV and Kasperskiy do. Please read this http://forums.winamp.com/showthread.php?p=2688962&posted=1#post2688962. I have installed ClamAV and Avast. Swichin off ClamAV makes winamp startup much faster.
I found that ClamAV checks some temporary files during winamp's startup in folder user\AppData\Local\Temp.
I'm not sure that adding the whole user\AppData\Local\Temp to the list of exceptions is safe...
Winamp takes to start up long time about 15-20 seconds. Only swiching off ClamAV helps reduce that time to 1 second. Datailed discussion here Winamp Forum