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3. Is there any commercial software that comes loaded with at least 500 sound effects? I know some softwares include many music loops but not sound effects.
    

I have a CD I bought in a retail store a while back, perhaps 4-5 years ago, called something like 6000 clips. It has 6000 sound effects, from explosions to cars and traffic to aircraft and windy/rainy weather stuff like lightning. You can hear some in http://www.thebest3d.com/dogwaffle/art/animations/canyonflight/canyonflight4.mov

I don't recall off the top of my head where that CD product came from but a Google search for 6000 sound clips might reveal it.

You might want to search gamedev resources too. They often have collections to sound effects. Try www.garagegames.com  and www.3dgamestudio.com  for example