3 beeps on start up

hello can anybody please help.
My imac g4 (tilt and swivel version) when I try to start up it beeps three times and does nothing just a black screen, I have taken out the new memory I put in six or so months ago and it does the same without it and I also took out the internal memory and gave it a good blow and around the slot I blew it then reseated the memory and it still does nothing, I have also tried resetting the p and vram but still the same three beeps my next option is to buy a new pram battery?..... anybody suggest other avenues to try before I take it to an expensive place for a repair.
Thank you very much for any help you can give me

1 beep = no RAM installed
2 beeps = incompatible RAM types
3 beeps = no good banks
4 beeps = no good boot images in the boot ROM (and/or bad sys config block)
5 beeps = processor is not usable

can anybody tell me if I can boot this imac up as a target drive? by holding down 'T'...... hopefully this is the case and I can salvage the contents of the computer?....