On a work iMac 27" Intel i5 that wouldn't boot when I got it. Did a restore to Yosemite. Tried to install El-Capitan, which didn't go well at first (I would download it and then get a message telling me it was corrupt when I tried to install). This morning, I re-downloaded and the install kicked off (progress!). However, it stalled and now shows the grey apple and a progress bar (about 95% completed). It's been like that for hours.
I tried to re-start but it goes right back to this screen. I ran disk utility, but nothing came up.
I'm not a mac user, so I'm not sure what steps to try next. Do I need to do another restore to Yosemite?