CS3 Photoshop cant read raw files

can anybody help

i have powerpc G5 mac os x 10.5.8 cs3 i have downloaded almost all of the dng files and camera raw converter 4,5 4,1 4,6 4,4,1 and photoshop keeps telling me it does not recognise the files. i still cant open up raw files. I have a conon 500d can anybody help

thanks

nicki