In the past, when I downloaded Mavericks, I was not given a choice about the destination drive. I could only target the drive I was currently booted on. I am having problems on my iMac. The tech support people at Alsoft (DiskWarrior) analyzed error messages I showed them and said the best solution was to wipe the drive clean and re-install Mavericks. How do you connect to the App store if your main drive is erased? No OS, no Safari to get online. I have two ext drives that can boot. But how do I funnel a new OS to another drive? In this case, the 1Tb HD on my iMac. The iMac doesn't have a DVD slot, so it is the App store online, or nothing. I'm also concerned about having TimeMachine do a Restore for all my data files and system preferences/passwords, etc. Will those old OS settings pollute the new system?