Q: It's not work for me , tel me when exactly i have to hold D keys? i have Macbook Pro wirh leopard

Restart and press it when you hear the startup tone.  Hold it until apple logo.

You may have to use one of the original install disks which have the directions printed on them (for the AHT). 

Ciao.

6: Hardware Test

Category: Hardware only related

Description: Apple's Hardware Test, does a internal investigation for hardware related issues.

Instructions: https://support.apple.com/kb/ht1509

For those machine that have it, you need to have a Internet connection and hold the D key down for quite some time to load it from Apple's servers.

If it gives anything, write it down and consider taking it in for service.

Find the closest Apple repair or distributor:  https://support.apple.com/kb/HT1434

Step by Step to fix your Mac

I had that problem; if it's going to work, hodling down the D from the time you hear the chime until either the Apple or a menu comes up will work.  If that doesn't work, you'll need to put in the install disk and then reboot and press the D from the chime.

I can't tell you how many times I tried just holding down the D!