It sounds like you are trying to install the Mavericks OS but get this error message saying the disk cannot be used to startup the computer. I found this article for while researching what might be happening here named:
OS X Lion: Installer reports "This disk cannot be used to start up your computer"
If that does not resolve the issue I would next try a safeboot, then try the update again:
Mac OS X: What is Safe Boot, Safe Mode?
Safe Mode is the state into which you can start up your Mac by performing a Safe Boot. To perform a Safe Boot, press and hold the Shift key immediately after your Mac starts up. Continue holding down the Shift key until a gray Apple logo appears on the screen.
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