computer keep restarting

everytime i install NORTON PERSONAL FIREWALL 2003, it asks to restart my computer to finalize the installation, so it restarts,a nd then never gets back into windows, it will get to the WINDOWS 2000 loading screen and after that, (when its suppose to go into windows), it will just restart, i cant get into windows, so i ended up formatting my drive 2 different times, please help, and let me know what the problem is, thanks a lot