how do you disable the alarm on a 2000 Volkswagen Passat.

You can also try recharging the battery. Some vehicles will not let you start them if the battery voltage is low. If you're going to remove the battery for charging, plug in a memory saver device to the vehicle before you disconnect the battery. Some vehicles require the computers to be powered up at all times. Otherwise you'll wind up being towed to the Dealer for a flash (reprogram) of the computers. Hope that helps! Jim

If the battery went dead then it needs recharged then the security system reset, now this maybe listed in the owners manual if not try this: lock all the doors from the inside manually except the drivers door, with key in hand exit the vehicle and using the key lock the drivers door, wait 5 minutes then using the key unlock the drivers door and see if it will start and run. If it won't run then either a good locksmith or the dealer needs to do a complete reset of the security system. Locksmith will be cheaper and most will come to you.