When that happens, I usually just replace the power supply. But it is always a good idea to occasionally blow the dust out of the machine, and fan. Replacing a battery for the clock is a good idea too. Get the right type.
I buy only Win 7 machines, which are available from many sources, including local computer builders. I have a Win 10 laptop I use occasionally so I could evaluate it, but I don't like the way you have to surrender your machine and data to Micro$oft. Yes, you can limit that, but it keeps nagging. And sometimes the upgrades can disable functions you've made custom settings on. As usual, Micro$oft has "enhanced" the experience by renaming and moving long standing features by burying them one or two clicks further down the menu tree.
BTW, I prefer Office 2003 (no ribbon), which officially isn't recommended for 10, but installs and works very well. I buy copies online cheap. The ribbon reminds me of the old WordStar menu, which dropped down and covered what you were working on. A LONG time ago, I worked in the newspaper biz, and when we converted to photo type setting, the commands were buried between the strings of copy. That is still essentially how it's done, certainly with html.
The more I do, the less I accomplish.