If your desktop or laptop is running very slow. It is taking minutes to boot up and shut down, this upgrade may be what you need. I am not talking about adding ram memory, new processor. Those all "feel good" upgrades. After you did that, theoretically you have a better system, but most of the time, it is hard to detect how much better your system is.
I am talking about replacing you traditional spinning type hard drive to a Solid State Drive (SSD). If your system has SATA interface or later (desktop or laptop), it is a very easy upgrade. I have an eight year old laptop. I just replaced old hard drive with a 1 terabyte 2.5" SATA SSD. The cost was just slightly over $100. There are newer and faster and different type of SSD's, but that is beyond the scope of what I have done. The SSD has given the laptop new live immediately. The improvement is very noticable. It used to take me 3 to 4 minutes to boot up and about the same amount of time to shut down, Now is 1 minute or less. Just add up the time you can save for doing other tasks rather than looking and waiting at computer screen.
My last client, the developer laptop they provided me was so slow I picked up a SSD on my lunch break and had their IT department swap it out and copy over the old drive. The only downside was the SSD became the property of the client, but the increase in speed in compiling, and overall performance was worth the investment.
-- "Democracy is the theory that the common people know what they want, and deserve to get it good and hard." - H. L. Mencken
6 years after installing an SSD it still only takes about a minute to boot my system...shutdown time has increased a little. Pay more attention to backups now because, apparently, retrieving data from a failed SSD is more problematic and costly than retrieving data from a failed conventional drive.
RE: Defrag Defrag has been a useless buzzword type utility for years. Moving fragmented files to a contiguous file speeds up the load from hard drive to RAM by such an infinitesimal amount of time that it doesn't even give you back the amount of time your hard drive is inaccessible during the defrag. The reason to not defrag a SSD is not for the a reason of utility. It is because SSDs are finite and a defrag will expend so many write cycles you actually shorten the life of the drive. I have always just laughed when people talk about the two minutes faster their PC boots. We are old and retired. What does that 2 minutes mean? Turn your computer on and go make some tea.
I once worked at a law firm with a very busy help desk and it got to the point where the agents were telling users they needed to defrag their hard drive just to get them off the phone. Meanwhile that also rendered their computer useless for the 45-60 minutes it took to run that defrag. And the ridiculous things was that the users all stored documents on servers, not on their hard drive. I once asked one of my techs why they told the user to defrag. I asked her to explain to me the science behind defragging a local hard drive to resolve a problem with a document stored on a server. Her reply was "It doesn't really but she's a royal pain in the *** and that gets her off my phone for an hour." That agent became unemployed at the end of that day. My agents will not ever refer to a user as a "PITA". And that was really awful technical skill on display right there. At our meeting that Friday I made it clear that the practice of making defrag a troubleshooting step would not be entertained any longer.
But I digress.... Yes, don't defrag a SSD, and that's why. You have a limited amount of writes on that drive. That number is very high, but it IS finite.
The average US male life expectancy is around 76 to 79. I believe Covid-19 dropped that by 1 year. I think when you are over 76, every minute should count. You better spend time on something you enjoy doing. Watch the lawn grow or computer to boot are not mine. It is okay to do things or enjoy a cup of tea leisurely. But I would rather use a 1500 watt electric tea kettle to boil the water than using a candle.