screen

Hi, I wanted to play a newly acquired Super Mario galaxy II and at one point I was informed that I could switch to 60 Hz. I followed the instruction and went to the general menu settings of the screen and chose 60Hz from the option available. My screen went grey even though everything else...

Foolishly playing with settings on plugging into HDTV for first time selected 60hz to see what it was like.......TV doesn't recognise signal and now cannot see menu options to set it back... Tried soft and hard (cut power) options with no joy. Can anyone suggest a fix? Thanks