Hi, I just upgraded my mid-2011 21" iMac to El Capitan. Although decent for every day use, I do a lot of video editing on the machine, which has made it quite sluggish recently. Still, it's been working fine, if a little slow at times. El Capitan, however, has completely destroyed the machine and I'm kinda panicking about the fact that I can't get any work done until it's fixed, so any advice is appreciated. After upgrading, I found that Safari tended to crash every ten minutes or so and I would have to force quit and relaunch. It seems to be doing okay right now, for once. When I first tried to launch iTunes, it took three attempts before a window would even open—both previous times it crashed. I haven't yet been able to use spotlight as it's too slow—the longest I waited was a minute, after results for a one-word query didn't appear after sixty seconds, I gave up. When I click an app, it's minutes before it finally opens. Most importantly, Final Cut Pro X. I have a lot of work I really need to be getting on with inside that app, but after about ten attempts at launching it, it crashed every time and I gave up. It wasn't up to date at that point, so I've now updated it (took about three hours for some reason) and when I launch the app, I'm asked to update the library. Clicking okay freezes the app, crashes it completely. Basically leaving me without access to any of the work I need to do. This is driving me crazy but it's obviously not entirely down to the operating system, so what could be contributing to this? Is there anything I can do to speed the machine up? Sorry if I failed to explain anything well.