Why doesnt my PS3 work after being on an HDTV using an HDMI cable?

My ps3 used to work on a normal non-HDTV... I then switched it to an HDTV using an HDMI Cable (instead of the 3 colored - Red, Yellow, and White plugs). Now that I'm using a non-HDTV again, the ps3 is not working with the colored plugs. when i first used the HDMI Cable, the ps3 asked, "Would you like to format this system to be in HD" (or something along those lines...) and of course i said "Yes!"... is there any way to convert back into non-HD format sop that i can continue to play the PS3!!?!??!?!?!