|It seems to me that there was a fault with either the socket or the headphones which has zapped something in the computer - unusual though.|
I suppose it could have just corrupted the software. With the appropriate F key try to get into BIOS. If you make it then it is still possible that Windows software has corrupted and there might be a way forward. If you can't get into BIOS and never ever see anything at all on the screen then might first paragraph applies.
Always pop back and let us know the outcome - thanks