You need to give details of how your attempts failed.
Some picture of what you are seeing would be handy.
click on this icon
pick this path...
Maybe your are getting the firmware password? Do you see this image?
Here's the instructions if you have the discs.
Mac OS X: Changing or resetting an account password
Changing your administrator password
Here's one method to reset the password without the install disc:
1. boot computer and hold the "apple" key and the "s" key.
2. wait for terminal show
3. release keys
4. type without the quotes: "/sbin/mount -uaw"
5. press enter
6. type without the quotes: "rm /var/db/.applesetupdone
7. press enter
8. type without the quotes: "reboot"
9. press enter
This will let you create a new admin account when you reboot your computer.
Also, without the discs, look at Mac OS X Tip - No Password, No Root, No CD? No Problem.
Here is a way to get around not knowing the admin password on Macs.
To reset your OS X password without an OS X CD you need to enter terminal and create a new admin account:
2. Hold apple + s down after you hear the chime.
3. When you get text prompt enter in these terminal commands to create a brand new admin account (hitting return after each line):
* mount -uw /
* rm /var/db/.AppleSetupDone
* shutdown -h now
4. After rebooting you should have a brand new admin account. When you login as the new admin you can simply delete the old one and you’re good to go again!