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.