OS X Yosemite installation failed

Trash the installer and re-download it. You have a bad download.

Then the alert may be for your current version. If you purchased the computer from another party, then you are still using that persons copy of OS X purchased under their Apple ID, not yours. In that case you need to erase the drive and reinstall the OS X version that came with your computer on two gray-labeled DVDs. Upgrade that to 10.6.8 then try installing Yosemite.

I get the exact same error. I'm on an iMac. I trashed the installer. However, when I log into the Mac App store to download OS X Yosemite again it says "downloaded". The App store will not allow me to download it!

I am having a similar failure. I have just swapped my upgraded memory back to oem (I upgraded to 2x8gb pny) so far the install seems to be progressing further, but I will know for sure in 20 min or so. Thanks for posting this! you may have saved me spinning my wheels for a while. I will post back to confirm.

Success!

The upgraded ram was the issue, I put back in the memory chips that came with the mac mini and it installed fine. After the install I put back in the PNY memory and its working as expected.

Thanks!

Did you download the file again after changed the updated RAM with the OEM because I had upgraded too to 8GB now I've put the old ones in and I STILL GET THE ERROR !

Well no worries ! I downloaded Mountain Lion from the Mac App Store and made a boot USB drive then I clean installed it on top of my Mavericks OS which was deletedand the downloaded Yosemite which then installed just fine without the above mentioned error ! I suggest you try this too while you have replaced any upgraded RAM with the OEM.

Kappy

"Then the alert may be for your current version. If you purchased the computer from another party, then you are still using that persons copy of OS X purchased under their Apple ID, not yours. In that case you need to erase the drive and reinstall the OS X version that came with your computer on two gray-labeled DVDs. Upgrade that to 10.6.8 then try installing Yosemite."

I believe that is my problem however i don't have any "gray-labeled DVDs" that came with the mac. Now what do i do?

Then if your computer is from 2011 or later you use Internet Recovery for OS X:

Install Mavericks, Lion/Mountain Lion 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 Lion/Mountain Lion. Mavericks: Select Reinstall Lion/Mountain Lion, Mavericks 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.

Just try to set right date and time using Terminal application from Installer (menu Tools - Terminal):

date {month}{day}{hour}{minute}{year}

e.g.

date 1122230214