Let Windows start in Safe Mode. (That's what it's there for). When it does, shut down your laptop, wait 10 seconds and then reboot it. That might fix the problem. If it doesn't, enter Safe Mode again and run System Restore.
Running System Restore (and choosing a date before you installed Zone Alarm) will efectively uninstall Zone Alarm. You can either re-install it or, if you'd rather avoid Zone Alarm, try it's main (free) rival, Comodo:
http://www.comodo.com/
Chris