Seriously, check out Reaper - it has everthing ProTools has plus everything Cubase/Nuendo has - VST/VSTi/DX/DXi/dpc powered plug-in compatability, 64 bit, ultra low latency engine, can mix up and use multiple file types in any project - (wav (all sample rates), mp3, wmp, midi, etc). unlimited tracks, loads of cool plug-ins (cmopressors, EQ, chorus, reverb etc etc) - installer only 3MB and its VERY easy to use.
This was made by the guys who created Winamp - the forum is very active and the developers actually answer users questions on a daily basis - there are also new updates daily so it can only get better... best of all its free but if you like it you should make the 'donation'.