Here are some various solutions I got from the 'net
a) From the Tile Doctor: (if you're going to tile) Clean as much of the glue as possible off the floor with a razor scraping tool. Carefully clean the concrete with a grease cutting cleaner and rinse allowing it to dry completely.Test the floors ability to accept tile by placing regular tap water on the concrete surface. Watch to see if the water absorbs into the concrete (concrete turns dark and water leaves the concrete surface).If the existing conceret will take in water, then it can be tiled. One caution however, use a latex modified thinset to enhance your bond strength and try to achieve at least 80-100% coverage on the back of the tiles after beat in.
B) From http://www.econcrete.info/_disc5/00000135.htm. Apply adhesive remover, scrape off what you can...then use a floor machine and and diamonds (~50 grit) grind the entire surface...if you want a smooth finish, step up to 120+ grit
c) Sand blast or pebble blast it
d) freeze it then scrape it
From my own experience....Do Not use 747. It won't work...Do not ask for advice from Home Depot. Also do not try to use a rotary floor machine with heavy sandpaper...the glue melts, causes slippage and you will be attacked by the rotary floor machine and end up highly torqued (excuse the pun). Do not rent anything from Taylor Rental in Moorestown , NJ.
Use a razor scraper with a long handle and be prepared for a workout..You might try softening the glue with a vinegar and hot water solution to soften. Get as much as you can off and once you are totally exhausted and frustrated, it's time to tile it over.
Another idea: You might try some of that orange stuff...it peels paint off wood better than zip strip. Be sure to wear a mask during..especially if the glue is old and might have asbestos in it.