Here's a manual on using manual activation:
(1) Start Mount&Blade, press "Enter serial key" button, and then select
"manual activation".
(2) Note down "Hardware hash" code displayed on the window.
(3)Open up an internet browser and go to "www.taleworlds.com/act/".
Enter hardware hash you obtained at step 2 and your serial key. The page
should then give you a 32-digit activation code.
(4) Enter the activation code you obtained at step 3, on the manual
activation window of Mount&Blade.