I have a five-year-old Dell laptop. It orignaly came with W7, and about a year ago I did the upgrade to W10. A couple of weeks ago it started getting very sluggish, and I had a friend who is computer knowledgeable take a look at it. He tells me that the problem has to do with having missed an important upgrade, which was provided at about the time I converted to W10, and that he has been unable to find a way to go back and install it. He says that, as a result, whenever new upgrades come down, they are going to screw up the computer He has it running pretty well now, but guarantees that it will not last. Having tried everything he knows to do, he says that a clean re-install is the only remedy, and I believe him. Since I installed the present W10, I assume that the necessary program for a re-install must be on the computer, but I do not have a clue as to where to look for it. Would very much appreciate any help anyone can give me with this. I have an external hard drive on which all of my files are backed up. I am anxious to get on with it, while the computer is still behaving itself, so will monitor this thread closely. Thanks in advance for any help.