TG,
the bitdefender free edition 7.2 indeed is on-demand only. It has no resident guard but offers regular updates. Thus I haven’t experienced any slowdown or other av-related problems on my machine. (WinXP SP2) But as eddy suggested you might want to try an online scanner so you actually don’t have to install another av.
All I can say is that the combination of avast/bitdefender works fine for me. :wink:

edit:
By the way you can always go for avast+bitdefender+online-scan+ … ::slight_smile: