My 2009 iMac (10.11.6 OSX 21.5 inch) freezes apparently randomly, even when using only Safari or Firefox apps. The mouse cursor will move but clicking doesn't do anything so I have to manually turn off and then turn on the computer. The temperature (measured with a kitchen probe digital thermometer) of the top of the computer goes sometimes to 110 F. But I took the computer to the Apple store genius and he checked it out (especially the fan) and said there was no problem, possibly because in taking it to the store I had to unplug it, which he said sometimes solves fan-type problems. The genius said the temperature didn't seem abnormally hot. I've tried the unplug-and-wait-five-minutes solution and even have tried parameter resets, but the problem of freezing continues. My memory was partitioned with a big chunk reserved for a virtual PC (Parallels software) that I never use now, so maybe that's part of the problem. But more than half of my terabyte of memory is "available." I'm not sure if buying a new iMac will solve the problem if it's malware in one of my files that would be imported into the new iMac. I'm tempted to get a new iMac since my 2009 one is getting pretty old, but I worry that I'll end up with the same problem if I do. Any advice?