Dell studio XPS, RAID, Windows 7, Slow start up, Very slow performance, Problem just started 5/21/2016

I am not well versed in fixing problems, looking for suggestions on how best to have the problem resolved. On 5/21/2016 the Dell studio XPS started slowing down, running slower and slower until a keystroke would take over 30 minutes to execute. The computer has a RAID hard drive configuration. The only change to the computer was Adobe Acrobat Reader DC downloaded. Everything was fine prior to this download. This may be a coincidence. The problem is this: When starting the computer it will take 350 to 400 seconds to get from power on to the desktop. The computer will operate normally for 10 or 15 minutes. After that period of time the computer becomes slower and slower with each task performed. It is a gradual degradation of performance. I have experienced a delay in shutting down Firefox or Photoshop of 30 to 45 minutes from the time I click the Red shutdown X to the time the desktop is empty and I can click on something else. I will do a shut down at this time. After a few moments I can restart the computer and when I get back to the desktop the performance is back to what I would expect when things were normal prior to 5/21/2016. If I continue working the performance will again begin to degrade until nothing can be done because actions take 30 minutes or more. I was able to run Trend Micro to scan my drives. Nothing was reported. I loaded MalwareBytes and ran that. Again, nothing reported. I got tech support at Trend to go into my computer and trouble shoot. The tech found no malware, viruses, etc. The tech disabled Trend at determined that Trend was not the cause of the slow down in performance. As the machine slowed down the tech looked at processor and memory usage. As the machine was bogging down the processor never went above 20% and the RAM never got above 3 gig in use. He said the performance was using very little of the resources and he had no idea why the machine was so slow. He directed me to this resource in Microsoft. I ran a check disk and nothing unusual was found. I checked defrag and that was at 0%. So it appears the machine runs very very slowly but it is not using any resources like something in the background is running full bore and using all the resources. The computer is 5 years old and is used mainly for Photoshop and Photodex. Any ideas what might be going on? Is this degrading of performance an indicator that there is undetectable malware present? Is there a hard drive failure in one of the RAID drives that is getting worse? I have an Acronis 2014 back up of the system on an external hard drive that was done before the issue appeared 5/21/2016. Should I take the computer to the shop and let them upgrade the drives? If it is a software issue, would reloading Windows 7 restore performance dependability to the levels I had prior to 5/21/2016? Would upgrading to Windows 10 resolve the issue? I am looking for suggestions from you good folks to figure out how to get the computer restored so I can get back to work on my graphics. Like I said, I am a klutz with virtually no computer repair and trouble shooting skills. Any helpful suggestions would really be appreciated. Thanks so much. Rich