I haven’t used my Macbook Pro from 2010 for the past two years.  When I last used it, it was crashing all the time.  I need to use it again so I got it fixed. It Needed a new Logic Board to fix a graphics issue (NVIDIA GeForce GT 330M driver was crashing).  The hard drive and battery were dying.  I got those three items replaced.  The new hard drive came with Snow Leopard (10.6.8) the version that was on it before.  I was going to upgrade it to El Capitan but thought I’d wait until I absolutely had to.  I have a USB video adapter to allow me to plug in a second external monitor (only have 1 mini-display port). Drivers for the dongle are only supported up to Snow Leopard. I don’t like the version of iMovie that comes with Snow Leopard, that’s the #1 reason I would want to upgrade the OS, but I upgraded our other 2010 Macbook Pro 13in 7,1 to El Capitan and can do video editing on that.

Of course I lost my Boot Camp installation so I won’t be running Windows 10 on it anymore.