for me it doesnt work , I hold the D key , but nothing happened :( , what should i do to check my Hardware ?

Welcome to the Apple Support Communities

Insert the Applications DVD that came with the computer and press D key when your Mac starts up

Try option d.

This will attempt to load an Internet version of Apple Hardware Test.

If this still does not work, you must boot from your original Applications DVD. It is the one bearing the text "AHT version xxxx" on it.