Ok as for the engineering facts about fire making building collapse...It can happen. All the fire has to do is get hot enough to be at or near the melting temperature of steel for the building to collapse.
Steel often melts at around 1370 degrees C (2500°F).
http://education.jlab.org/qa/meltingpoint_01.html
typical flames
Oxyhydrogen Flame (2000 °C or above)(3645 °F)
Bunsen Burner Flame (min. to max. setting) (1300 to 1600 °C)(2372 to 2912 °F)
Blowtorch Flame (1800 °C)(2370 °F)
Candle Flame (760 °C)(1400 °F)
http://en.wikipedia.org/wiki/Fire
As for the US consiperacy theory if 9/11 I say its just rediculous and stupid. If the american populous or even the world found out they did, there would be hell to pay and the american credibility would be shot.
The media comment, well I don't usually watch them, but when I do it seems that they never show all the facts or they get them wrong (not all the time, but it does happen). Local ones might be different, but if something happens in the world I'd probably go to CTV news then CNN. Again I don't watch so I culd be very wrong.
Finally about the US misleading the world about WMD's in Iraq and the link to 9/11...I'm still waiting for news about any found and the link. Its possible I could have missed the news cast how ever...