Hi,
there is a different manner for IM provider in Win9x based and WinNT based systems. On WinNT based systems avast! tests file-operation in running IM programs (when you are receiving a file, IM program is writting data to disk and in this moment avast! tests it). The situation on Win9x systems is different. There are 3 types of protection: ICQ - avast! uses ICQ API to determine that file is received - and ashQuick is executed; YAHOO, AIM, TRILLIAN - avast! holds settings so that these programs tests received files via ashQuick.exe. Other IM programs (MSN, Kazaa(Lite), DirectConnect(++), BearShare) are guarded through "testing received files folder" - avast! always checks CURRENT folder for this programs, so you can change if from default - it's no problem.
pavels