(edited slightly)
<< The average fighter in the Taliban does not want to be there. They are forced to be there because to walk away is sure death. They stay because the leaders of the Taliban regularly kill people in public displays in order to terrorize their people. This is no different than the soldiers of Iraq. They do not want to be there, but have no choice. All of the problems compound to a pretty lousy fighting force. >>
Well, the core of Taleban force are the religious fanatics. They are nothing like the iraqi forces. Iraqi were demoralised, they did not want to fight. Taleban is extremely moralised. Fighting against the unbelievers is a sure way to gain attention of Allah. If they die doing so, so be it, they will gain their acces to Paradise. Point is, unlike iraqis, they are not afraid to die. Enemy that has no regard for his own life? That's the worst kind of enemy, just ask the marines who assaulted Tarawa, Iwo Jima, Okinawa...
What would I do? Well (assuming USA had the full backing of neighbouring countries)... First, send in the Special Forces. Hit Osama Bin Ladin and his men. Hit them hard. Taleban will propable protest and attack american they can find (inside Afganistan that is). In best case scenario, conflict ends here. If not... Then, send in 30.000 - 50.000 men (more if needed) supported by combat helicopters, APC's and tanks. Maybe some NATO forces as well (british mostly) Use good men, marines would be suitable. Depending where you enter the country, try to make contact with the government forces in the north. Together with them, drive to Kabul. Surround it, and neutralise it. Pakistan is a big mystery here, so make sure that Taleban has no route there (just in case), cut their supply-lines.
You would then propably have only western Afganistan to worry about. If Iran decides to hit Taleban at this point, let them. In best case, Taleban gets crushed between NATO and Iran.
Anyway, at this point you could reduce your troops. Arm the government troops and support them, they should be able to take care of the weakened Taleban.
No collateral damage! The majority of people of Afganistan will propably welcome you as liberators, make sure you win their hearts.
After the war it's imperative that Afganistan receives aid! They must feel like that they have been liberated! Civilans must be helped, infrastrucure restored. And relations between you and Iran might improve. "Enemy of my enemy is my friend".
Well, that's just me...
EDIT: Well, you might need more that 30.000 - 50.000 men.