HELP...! HELP...! Honda Civic HX 2000 will not start?

Do you have an alarm? I had a aftermarket alarm installed in my old Honda and i had the same thing happen to me(besides the P and D light blinking though 'cause it was 5 speed). The alarm somehow went on the fritz when i changed my battery and was acting like the car alarm went off,the lights were blinking and the engine wouldn't start.Didn't know how to fix it so i ended up finding the alarm unit and disconnecting it. Not sure if that's your problem but it is similar to mine and that is what fixed my problem. Hope this helps,good luck.