Engine light currently on won't go off

Yesterday I replaced the old champion spark plugs with new Bosch platinum spark plugs (i'm sure they are the right ones for the car) Also I replaced the old Fram air filter with a K&N airfilter. yesterday put about 100km (60-70miles maybe?) and everything seemed to be fine. The engine light wasn't on. Took it to work it was fine. Halfway back home form work the light came on. I have an idea of what it is (the spark plugs) but I don't feel like spending 20 minutes or so on spark plugs (very hard to get to and work with because there in an awkward spot) if it might be the airfilter or something?.....

I tried resetting my cars computer today, while the car was off I unplugged the negative wire to the battery and pressed the brake to release all electricity that may be in the car. I let it sit for about 5 minutes started it up still a check engine light. I did the same thing again drove it around, still a check engine light. then I removed the negative flipped the lights to the on position left the lights switch to the on position with the negative wire off for about 10-15 minutes turned the lights to the off position, reconnected the negative wire to the battery started it up still a check engine light. The gas cap is on tight too. I'm starting to think it has something to with the airfilter maybe? because I don't see how it can be the spark plugs considering the engine sounds fine, actually better becasue since I've done it an annoying noise has dissapeared. Any help at all little or big is greatly appreicated.

Check the gap on your plugs.
Might be a missfire.

Thanks Robbie but I already got the light out had to take it to the garage to get the computer reset I don't understand why the battery technique didn't reset the computer. Oh well alls better now.

OBDII cars (96-up) require a scan tool to clear the codes. Save yourself some money next time and take your car to Auto Zone, they will clear your codes for free. I hear Advance Auto Parts is starting to offer this service too.

Yeah I already went to the garage and got it reset. I live In canada so I can't go to autozone. Canadian tire is selling a tool the can reset the codes for only $145 about $100 U.S. I think I might just go out and buy it.

Im having the same problem with my sunfire(02) but the ETC(Enhanced Traction Control) light is on too. Im thinking it may be the air filter too but if not its off to Autozone. Any suggestions ?

Im having the same problem with my sunfire(02) but the ETC(Enhanced Traction Control) light is on too. Im thinking it may be the air filter too but if not its off to Autozone. Any suggestions ? My sunfire (and also my parent's van) had that problem, they spent thousands, turns out it was just sensitive to condensation and wanted gas line antifreeze (with respect to the engine light problem) Its worth a shot!