immobiliser?

how do i reset my immobiliser on a lexus is200 (2000)? i had problems after i was out of the country for a few weeks and the battery had run down (now charged) and also the alternater fuse (now replaced) had blown upon attempting a jump start. now i have power to my car but it seems as if the immobiliser it preventing the car from turning over. what do i do????

laurie mclellan
January 2009