How do you remove a 1991 Ford Radio...

this is a stock AM-FM Cassette deck...
and it has some small round holes (4) on each corner...


There must be a trick to the removal ... for even taking apart much of the dash did no good...the radio does not work and I thought I would replace it with another Ford radio..

Please help...thanks...

Are there two holes on each side of the faceplate? If so, you need a special radio removal set - looks like two u-shaped hefty wires. such as these:
http://www.walmart.com/catalog/product.gsp?product_id=870835&cat=4429&type=19&dept=3944&path=0%3A3944%3A3947%3A4429

can also cut and bend a metal coat hanger
push the ends in the holes and pull forward on radio
may have to wiggle on cat hangers a little to get clips to release