Q: Have a 2007 imac running mavericks and want to change ownership

You need to boot the machine with the original install disc, wipe the HD, reinstall the OS, and then update/upgrade as desired. If you don't have the discs, call AppleCare and request replacement discs. Should be available for nominal S&H.

You need to boot from a retail copy of Mac OS X 10.6 (the original disk set was Mac OS X 10.4 or 10.5, not worth bothering with), available from the online Apple Store, erase the hard drive and install 10.6, then upgrade to 10.9 Mavericks through your own Apple ID. You can then reinstall any applications for which you received the installer disks or otherwise got the license, and purchase/download any applicable from the Mac App Store againusing your own Apple ID.

Regards.

The iMac you have came w/system DVDs.  See KB Article:  http://support.apple.com/kb/HT1159

You will need to get them from the person that gave you the iMac.  If that is not possible you can get replacement System Install & Restore CD/DVDs from Apple's Customer Support - in the US, (800) 767-2775 - for a nominal S&H fee. You'll need to have the model and/or serial number of your Mac available.

If you're not in the US, you may need to go through the regional Apple Store that serves your location to find the contact number. Here's a list of links to all of those - http://store.apple.com/Catalog/US/Images/intlstoreroutingpage.html Another resource:  International Support Phone #s.

================

After you receive the system DVDs read the info in the links listed below as they also apply to you.

What to do before selling or giving away your Mac

Preparing an old Mac for sale

How to prepare your Mac for sale

Clicky click--—> Erasing disks securely

================

Start up from your install disc, go to Disk Utility and select the disk and click erase - to securely erase data click Security Options and Erase Free Space which will entirely wipe your disk, overwriting it with zeros so that no data is recoverable.

See KB Articles:  http://support.apple.com/kb/PH10727 OS X Mountain Lion: Restore your computer’s software

http://support.apple.com/kb/ph11273 OS X Mountain Lion: Erase and reinstall OS X

http://support.apple.com/kb/PH6817 Mac OS X 10.6: Restoring your computer’s software

http://support.apple.com/kb/PH3840 OS X Lion: Restore your computer’s software

Good luck!