CCleaner is some software made by Piriform designed to (you guessed it) clean the C: drive. Back when it was first available to the public it would only clean the C: drive but now it can clean all devices attached to the computer, that includes external HDD, pen drive if it can be viewed in My computer it can clean it.
Not only can CCleaner clean any drives you have in your computer but it can also grant you access to the registry in an easier format for the standard user to understand so you can alter things (but if you don’t know what you’re doing I don’t recommend doing it). It also has a tools section that lets you change what opens on startup in greater detail than using the startup folder in the start menu as you can remove Skype using CCleaner but not the startup file.
If cleaning your C: drive is the main issue for you this is the best piece of software I can recommend because you can choose precisely what you want to be cleaned and what you want to be left alone, CCleaner can also clear any temporary files you may have in your computer (let’s face it, if you use it, you’ll have temp files). The RAM can be cleaned out if it is lagging behind so you can remove old files that you have used recently and the RAM wanted to keep close because you use them a lot.
If you want to know anything leave a comment and I’ll get back to ye. Thanks for reading