I'm trying to install Yosemite onto a 15" Macbook Pro / Late 2008 model with OS X Mountain Lion on it. I've checked Apples site and it says I can install Yosemite on this machine with these specs. When I click through the installer and get to my harddrive it won't let me select it and I get an error message that reads "This Disk is used for time machine backups" which it isn't. I have an external drive dedicated just for that purpose. I do not have the external connected when I try to install and I have time machine turned off in preferences. Also, my harddrive is not listed in the drive list in time machines preferences. I have no idea what's going on. I apologize if I'm missing something obvious. Can someone please help me? thank you, Justin
I had the same problem. Turned out it had once been used for backups. I removed the folder Backups.backupd in the HD root and everything went fine after that. I assume you have solved it, but I'm writing this in case somebody else have the same problem.
It's unlikely you'll need to go though those complicated steps in the answers above.
Are you running the Yosemite installer directly from the downloaded application? If so that is strange.
I would verify that your time machine backup is complete and then use a utility like Diskmaker X to make a bootable Yosemite USB flash drive and boot from that.
When you get through the language selection screen you can use Disk Utility (it's in one of the menus, sorry I forget exactly where...) to delete the current partitions, create a new one and then let the installer do it's thing.
When it is done, use your Time Machine backup to restore your apps and settings.
Get an 8+ GB thumb drive. Plug it in to your Mac, format it as HFS Journaled and name it "Untitled".
Launch /Applications/Utilities/Terminal.app, su as root, then paste the following command into Terminal:
/Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Yosemite.app --nointeraction
I forgot the actual file name, basically "/Applications/Install\ OS\ X\ Yosemite.app" should be the path to the installer.
Once this completes, reboot while holding down the Option key.
When you get the choice, choose the OS X installer disk.
Once you get to the setup screen, run Disk Utility. Format the target installation disk, using HFS Journaled. Once it's complete, quit Disk Utility. Then, kick off the Yosemite installer.