I'm trying to troubleshoot my daughter's 2015 21.5" iMac (8GB/3.1 GHz/1TB HDD, not Fusion Drive), which seems to be very slow. It's running 10.12.4 First, it takes about a minute to startup to the login screen, and then takes another 3 minutes to stabilize at the Finder. 1. Is a full minute from power on to login screen reasonable? 2. Seems as if 3 more minutes to system stabilize is excessive. Login items include Dropbox, iTunesHelper, Spotify, Show Desktop, and AdobeResourceSynchronizer There are many times when the beachball spins for a long time. It seems that whenever the computer is running a significant app (even if total CPU load is about 15%) everything else, from using Quick Look on a PDF, opening System Prefs or any other app, etc., takes a long time (up to a minute for to open System Prefs). Even the keyboard hiccups...while typing this post, the cursor often stalls, particularly if I backspace to correct an error). The iMac was set up initially by migrating (at initial setup) from a MacBook Pro. Short of doing a complete system rebuild (fresh install), are there some troubleshooting steps I can consider? Thanks.