Hi,
imho those files got onto your PC as archives and via an unsafely configured IE/browser
- Read VirusRemoval" below on how to secure your system & Browser(s) better, e.g. turn of activeX/scripting except for know, secure sites..
- avast resident shield doesn't scan archives in its default configuration (which is normally not necessary and would be a ressource-hog except on fast PCs)
-> ad-aware probably unpacked those archives for analysis, and that is where avast stepped in
-> in a full scan with archivescanning enabled, avast should catch the initial archives (as I gather it did?); if not, send them to alwil, please