So i just got my HDMI cable for my PS3?

May be...

and when i put the settings in for the ps3 for the HDMI cable its like it deleted everything i had saved all my demos all my songs everything what could have happend what did i do worng? lol

yeah you re formatted you hd I did it too when I hooked up my HDMI cable. it shouldnt take alot to get well most of your stuff back by logging onto your psn account and re downloading them again

You just reformated your PS3's hard drive accidentally since it wiped out everything you have before..

You could try calling Sony.

you can re download everything you payed for by signing onto your psn but as far as what you did you probably reformatted your hard drive or you may have corrupted your data and turned it off while it was accessing your info... good luck to you.