help need help badly

[YourCanadianPlug]

hello, this is my first time posting ngl im not that smart when it comes to tech. i was messing around with setting when my pc was connected to my tv. i accidently manually set my tv to 120Hz in the seetings on my pc, and then my screen went black, so i thought it was gonna change. now i only got On-Board Graphics and my pcs kinda old so it only got VGA right now, so i switched back to my monitor and searched the web for days finding nothing helpful, i really need help as im resulting to selling my 50" 3d tv because i cant use it and i had lost my job a week ago, sadly im fairly new to all this computer stuff (say like only 2 months of knowledge) so im stumped at this point. hopefully someone can help me.