Please try this:
-unplug the tv POWER cord from the wall outlet.
-press and hold the power button on the tv for 20 seconds and release.
-plug in the tv power cord and try to turn on.
If that does not help then unfortunately there is not going to be any easy reset/fix. The Tv has an internal failure and the back panel needs to come off, complex checks need to be performed with a meter, then parts ordered and installed. If that is something you want to attempt then reply back here and I can assist you further.
If you are unable or unwilling to perform any of these procedures then a repair shop should be consulted but I can tell you that diagnosis, parts, and labor will end up costing more than a new 42" Tv and could take a few days to weeks to get all sorted. I would strongly suggest you use the money you saved by coming here first toward a replacement tv rather than going for a repair.
I do understand that finding out your tv needs expensive repairs is not pleasant but please keep in mind why you came here to use this service.
An in home diagnosis by a local repair shop costs $100-$135 up front. Finding out whether your tv can be repaired and how much it may cost from this online chat costs a fraction of that. At least now you can make the most of your situation without high repair costs and long wait times.
Before you go please take a moment to submit at least a 3 star rating at the top of this page to show your appreciation for saving you so much time and money.