I'm trying to install Yosemite from the app store - when it asks me to "select the disk where you want to install OS X" it won't let me select Macintosh HD (my only option) because it says "This disk cannot be used to start up your computer" please help I don't know what is wrong!
MacBook Pro, Mac OS X (10.6.8)
http://www.apple.com/support/mac/app-store/contact/
27" i7 iMac (Mid 2011) refurb, OS X Yo (10.10), Mavs, ML & SL, G4 450 MP w/10.5 & 9.2.2
It sounds like your disk drive is not formatted for OS X. It must be formatted OS Mac Extended and GUID partition mapping.
Reformatting the disk drive will wipe out all data on the disk drive.
I have exactly the same problem. I have a MacBook Pro, Retina, Late 2013, currently running OS X 10.9.5 (13F34)
I have not messed with, added or repartitioned the hard Drive.
Macintosh HD:
Available: 184.83 GB
Capacity: 250.1 GB
Mount Point: /
File System: Journaled HFS+
Writable: Yes
Ignore Ownership: No
BSD Name: disk0s2s1
Physical Drive:
Media Name: APPLE SSD SM0256F Media
Medium Type: SSD
Protocol: PCI
Internal: Yes
Partition Map Type: GPT (GUID Partition Table)
S.M.A.R.T. Status: Verified
This worked for me trying to install 10.10 over a fresh 10.6 on 2010 MBA. http://support.apple.com/en-us/HT203482
Yosemite "this disk cannot be used to start up your computer"
