Downloaded Aircraft Won't Work

I've been downloading and installing airplanes for ages now and never had any problems. Recently I had to do a complete reinstall of CFS II because while trying to just find and install the Mission Builder from the disk because on an earlier install it didnt' take for what ever reason, the program desided all by itself to delete the whole sim. Christ, I was mad. There went all my addons: planes, effects, sceanery, bases everything. Thank you M$! 
After reinstalling the whole freakin thing I went to reload some of my favorite planes. The only ones I can get to work now are the 1% aircraft from AvHistory. Nothing from this site works.
Did the folks here change anything recently or maybe is there something I've missed?
My Winzip program hasn't changed so I don't think there's a problem there. I just downloaded these planes recently (mostly P-40s). Is anyone else having difficulties with these?
One other thing, When viewed from Windows Explorer my CFS II reinstall shows all the planes I had on the system before it got deleted even all the planes from "Defense of Australia", everything. I assume they were copied to my registery and reinstalled automatically but the problem is that they don't show from within the sim. All that shows there is the stock MS planes. Anyone got any ideas?
Thanks, L.J. Over...

After reinstalling the whole freakin thing I went to reload some of my favorite planes. The only ones I can get to work now are the 1% aircraft from AvHistory. Nothing from this site works.
Did the folks here change anything recently or maybe is there something I've missed?
My Winzip program hasn't changed so I don't think there's a problem there. I just downloaded these planes recently (mostly P-40s). Is anyone else having difficulties with these?
One other thing, When viewed from Windows Explorer my CFS II reinstall shows all the planes I had on the system before it got deleted even all the planes from "Defense of Australia", everything. I assume they were copied to my registery and reinstalled automatically but the problem is that they don't show from within the sim. All that shows there is the stock MS planes. Anyone got any ideas?
Thanks, L.J. Over...