Exchange 2000 SP3 Installation..

well guys..my exchange 2K server is installed on win2K server (SP 3 installed) where i m tryin to install Exchange 2K SP 3. when i select UPDATE on COMPONENT SELECTION screen it gives me error : YOU MUST HAVE EXCHANGE FULL ADMINISTRATIVE RIGHTS or SETUP IS UNABLE TO ACCESS THE WINDOWS 2K ACTIVE DIRECTORY or FAILED TO CONTACT THE SCHEMA MASTER SERVER FOR THIS ACTIVE DIRECTORY FOREST. I m having exchange full administrator rights, AD Connector upgraded successfully and my exchange is running so smoothly so i cant think about other 2 errors. what should i do?
IF YOU WANT I CAN SEND SCREENSHOT (jpg format) SO YOU WILL GET BETTER IDEA..