How to flash a droid to use Verizon prepaid
What carrier was the phone previously active on?
In actuality, you should have no problems activating any Droid X on Verizon, even aftermarket devices are easily activated, and my wife and I stopped using contracts and go prepaid now, and we both use the DX on VZW prepaid.
Just get rid of the usual activation screen by tapping the upper left corner, then right, then lower right and left (above the separator line) and the screen animation should bring up the sync menu.
You can set up your WiFi, Email and access your SD card and whatever you need before you dial *22898 and enter your current number, or you will need to have assistance porting your previous number from your current provider.