Completely disagree on that answer. The first rule in troubleshooting is to start with the most likely and least intrusive troubleshooting. The most likely cause of a slow boot is OS related. Check your application and system event logs for a service that is hanging or faulty application. I would also start by going into msconfig and disabling all non Microsoft services from starting at boot. If the Server boots fine after doing this, start the non-Microsoft services one at a time and then trying a boot until you find the culprit.