reset password and user imac os yosemite

Giving away / Selling your Mac / Resetting the computer to factory condition

http://support.apple.com/en-us/HT201065

http://www.thesafemac.com/how-to-prepare-your-mac-for-sale/

You need to completely erase the drive and install from scratch. If the computer came with installer discs, then start by booting from Disc 1, erasing the drive, then reinstalling Snow Leopard. You can also update the firmware for Network Restore: Computers that can be upgraded to use OS X Internet Recovery. Then you can do the following:

Install OS X Using Internet Recovery

Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.

Boot to the Internet Recovery HD:

Restart the computer and after the chime press and hold down the COMMAND-OPTION- R keys until a globe appears on the screen. Wait patiently - 15-20 minutes - until the Recovery main menu appears.

Partition and Format the hard drive:

1. Select Disk Utility from the main menu and click on the Continue button.
2. After DU loads select your newly installed hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed. Quit DU and return to the main menu.

Reinstall OS X: Select Reinstall OS X and click on the Install button. Be sure to select the correct drive to use if you have more than one.

Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.

This should restore the version of OS X originally pre-installed on the computer.

You want to re-reset the password, correct? And there's only one user account on there (the one you created)?

This is what you do.

1. Shut down your Mac.
2. When you boot it back up, hold down the Cmd and R keys. This will boot you into Recovery Mode.
3. From Utilities, select Terminal.
4. Then in the terminal, type resetpassword

The rest you can take from there, I'm sure.