Switch (swap) the wires at the window switch - to the motor / regulator.

See this URL http://www.google.com/webhp

Try this tip
First, check the battery and starter cables for their tightness or free of corrosion and physical damaged.

See this Starting system simplified diagram. Have a help from an assistant to crank the engine, use a 12 volt light tester or a digital voltmeter, apply it to the starter control circuit.
If there is light or 12 volts and the starter isn't cranking, then the starter is the culprit. Have the starter to bench test for free at the local auto parts stores.
If there isn't no light or no volts, then the ignition switch is the culprit.
Check the starter relay and position the Automatic transmission shifter in neutral.

http://www.samarins.com/glossary/starter.html

Note: a 3/4 charge battery is 12.50 volts
A discharge battery is 11.75 volts.
A battery under a cranking load and it is reading less than 7 volts,it will be a recycled battery.

Note : Ignition starter switch directs current from the fuse panel to other systems in the vehicle
When not replaced, vehicle may experience no-start, intermittent shut down and/or current will not flow to all systems.

Try these sources; www.NPD.com (National Parts Depot), www.rockauto.com, www.autokrafters.com (Auto Krafters), www.theautopartsshop.com, www.earlyfordstore.com, www.macsautoparts.com - to list only a few sources. You have a classic - keep it running! I also own a 1966 Ford Mustang - and have purchased from these vendors over the years.
They (Auto Parts Shop) list the window regulator (manual for left or right sides) from around $52.00 each for your vehicle.

Remove the inside door handle bezel first then release the perimeter clips. The panel will release by moving upwards starting at the rear. There are no screws, just clips and the bezel. Then of course there is a clip on the rod after the panel is off. And something about the armrest pull cup retainers on the inside of the trim panel. Needle nose pliers to compress those clips. It looks like there are 7 or 8 clips retaining the panel, hard to tell from my picture. here , this will help >> http://www.justanswer.com/.../...1-bonneville.html

See this website, http://boards.straightdope.com/sdmb/showthread.php

It could be its "off track" or it's an electrical problem.You also can find a tool check it: http://www.spobd2.com/

It's in the auxiliary relay box behind the glove box. http://www.spobd2.com/

The flasher for both the turn signals and the hazards are both integrated into the hazard flasher switch on the dash. The answer below from ella1234 is completely wrong so don't go looking there.