Disconnect plug C191 or whatever the engine loom plug is. It is located just below the throttle-body.
Clean the contacts, and pull the boot off of the engine loom side to see if there is corrosion or contamination.
No Main Relay.
The lack of switching voltage at the main relay suggests that your ignition switch may have failed. Look for exiting voltage as per previous poster's suggestion.
Test for continuity on the DME power cable.
No Power windows.
The unloader relay may also need to be tested or the power window circuit breaker(if applicable) may have been tripped.