How do I get a PS3 off HDMI when my T.V is HD??

** Please help** My brother-in-law bought a PS3 for my son but it can only be played on HDMI ready T.V's. Our's is HD only! I have access to a HDMI T.V so if I need to change setting's on HDMI T.V then it's not a problem. Please help as my 12 year old son is driving me up the wall! And it's half term!!!
Thank you for taking the time to read this begging question.

Frantic mum of bored 12 year old boy!!
February 2011