Why does my engine light remain on?

Not sure what type of car this is. So generally, this could be cause by a faulty fuel filter. They can get 'full' and block the gas from getting to the engine.

It sounds like you need a good tune-up, such as spark plugs and/or wires. They will act up when cold and when warmed by engine temperature will let the engine run smoothly again. And possibly a distributor cap/rotor.

serial number/keygen for registry reviver

The check engine will be on if the key is on but engine not running . This is normal. If the check engine goes out when the engine starts there are no codes present . Did you check the fuel filter . Sometimes when a filter is dirty there is sedement laying in the filter canister . When the pump starts working the flow picks up the sedement and plugs any remaining open screen and stops the fuel completely . The engine stops . When the flow stops the sedement falls back allowing flow again. and the engine will run for another while . If the filter is old it should be changed anyway . Also when the engine stops check to see if there is spark at the spark plugs while cranking the engine .

start with a tune up,

Is the check engine light on when the engine is running ?
It could be a bad injector that is flooding a cylinder, or not giving the cylinder enough fuel. Or it could be an electrical problem.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve but always run a OBD2 fault code as well as the cleaning procedure. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

The first thing to check is the ignition timing then the spark plug gaps. There are specific settings/size for the above and must be correct for the car to run smoothly.

The computer should reset itself after 100miles so that all of the systems recalibrate themselves to work properly after the battery is disconnected. If the engine was flooded it will start rough and may day when close to idle until it has completely burned off all of the flooded fuel. If there was any other fluid that reached into the engine ie.. water starter fluid which you SHOULD NOT use on a rotary engine and if you feel you must pease only use a very small amount one or two sprays, the car will run rough until whatever it is burns out. By 200miles you should be running smooth again.Iif there are any warning lights remaining on you will need to troubleshoot those and go from there.

disconnect batt. for 30 min. then reconnect,if no problem exist the lights will go away