How to increase the speed of my PC wihout upgrading new hardwares?!?

Create a partition and then store all the files you want to save on that partition.

Then reformat the C: and then reinstall Windows or Linux. Do a clean install where you have to go find the drivers, don't do a factory restore because it will reload all the unwanted bloatware. If you're using Windows 10 then use the Media Creation tool to burn a copy of the O.S. to a thumb drive.

I've tried all these things like clearing the cache, defragging, uninstalling unused programs but this is a band-aid and sooner or later the PC will run like crap again. Also, some programs and old drivers will leave remnants in the registry which can sometimes cause the system to slow down. At the same time it's a good thing to know how to manage and maintain your PC instead of leaving it a mess.

If your PC is slow because you have low end hardware or you have an old system then there is not much you can do without upgrading. People might hate the word bottleneck but bottlenecks are very real.

Also, if the CPU is overheating then your system will slow down. Pay attention to CPU and Video Card temperatures.

Unfortunately, there's really no legitimate way to increase the speed of your computer without upgrades... as you're no improving your system. HOWEVER, you can restore system performance (making your system running smoother & SEEM FASTER) by doing a few things.

FIRST, uninstall ALL UNWANTED OR UNUSED SOFTWARE -- If you're not using the software for one reason or another, it's just cluttering up your system & potentially gumming up the works. Software that is rarely used is stuff you'll need to seriously consider if you need to keep it around OR uninstall them & hang onto the installers when you need them later.

Second, clean up the Boot-up process. -- Programs that you don't need to start when loading up your computer is viable for removal. Security software (Anti-virus, ect.) should remain on that list, but any "helper programs" (which is a pre-loader for other software) are ones that are easy to cut out.

Programs that have an option to "Load at Start-up" (the program may phrase it differently) will need to be personally reviewed on a per-case basis. Programs that you use frequently, like Discord for example, may be useful to keep on the start-up. However, stuff you use occasionally or infrequently can go. You might be slightly inconvenienced that you'll have to load it up when you need them, but you'll free up resources that could be used elsewhere.

Third, clean out temporary files & junk... This is another common sense deal. Any old & outdated program installers can be safely deleted (unless you have a reason to hold onto them) OR offloaded to another storage medium (external storage device, CD / DVD-ROM, ect.)

For temporary files, you can use a utility program like CCleaner to find & safely delete these files. This can clear up multiple GB's when done periodically (or at least multiple MB's, if done frequently).

Fourth, clean up your system registry -- This is most just cleaning up errors & unused entries (from deleted programs & whatnot). As this is something that's a bit of advanced, I recommend utilizing a trusted utility program like CCleaner or Eusing's Free Registry Cleaner (EFRC) to scan your computer's registry & fixing (or "cleaning") entries that are safe to address.

Because of it's advanced nature, it's generally recommended to utilize back-up options with the registry so you can undo the changes, if needed. CCleaner will ask you if you want to make a back-up before it does it's cleaniner. EFRC generally utilized Windows System Recovery system for this, but does allow you to do a complete back-up of your system's registry manually (ideally BEFORE you start the cleaning process).

Finally, if you're running on any HDD's... Perform a MANUAL DEFRAG of your computer. -- As part of the traditional HDD's, your computer wants to read files in one pass. However, as the contents of the drive change (adding, deleting & modifying files), the HDD will eventually have to break up (fragment) your files into multiple chunks to fit in the spare spots on the drive. This will cause your computer to make multiple passes to read the file (as it has to jump around), which does slow down your system over time. When you defrag your drive, you force your computer to piece all the chunks of your files in order so it can read the files in one pass (or as few passes as possible, as it may not be able to fully defrag all files).

Windows 10 already has a disk defrag scheduled automatically as part of it's performance routine, so it tries to keep things together whenever possible. HOWEVER, life & your usage may get in the way, so it doesn't hurt to give your computer a little "Personal Downtime" & manually run the defrag utility.

IMPORTANT NOTE: DO NOT PERFORM ON SOLID-STATE DRIVES (SSD'S) -- SSD's work differently that HDD's as they can quickly access data from multiple locations, so it's not affected by file fragmentation & don't need to do this. In fact, your computer will warn you NOT to proceed on this & will try to prevent you from doing a defrag. The main reason is that file defragmentation causes undue wear on SSD's & runs COUNTER to the drive's wear-leveling mechanics (where the drive spreads chunks around to limit wearing out parts of the drive).

All these steps will help to optimize your computer's resources, which will make it feel that it's running faster (or at least smoother) than before. However, if you're still not happy with the results, there is still one option available for you...

REFORMAT YOUR COMPUTER & REINSTALL WINDOWS (OR YOUR PREFER OPERATING SYSTEM).

I know it an extreme thing, which why I'm reserving it as a NUCLEAR OPTION as it's going to cause some temporary inconveniences for you. BEFORE you do this, make sure you back up any & all files you want to keep on an external storage drive (like a USB HDD or a CD / DVD-ROM) first as this process will delete EVERYTHING from your system. This is something that's fairly advanced as well, so unless you're technically inclined... SEE EXPERIENCED OR PROFESSIONAL HELP!

By reformatting your computer & reinstalling Windows, you're effectively resetting your computer to it's original state... before your life "gummed up the works". Once done, install all OS updates & your security software first (as your first priority is to get your system secured) before moving all your backed up files & re-installing the programs you use frequently. By installing the latest version of your programs, you're starting at a newer base for future updates & so on.

PLEASE BE AWARE that all these options & steps will only make a TEMPORARY IMPROVEMENT on performance, as life will rear it's head again to gum up works once again (with new updates, new temporary files & whatnot) that will likely screw up your system's performance in hopefully new & interesting ways (as repeating old ways are boring & predictable). You will need to do maintenance periodically (like once every 3 months) to keep your computer's performance up.

Hope this sheds some light on the subject.

Many hints available on line if you search with DuckDuckGo or Google or others. Clean HDD, make larger page file, cut out unwanted programs loaded on power up, cool the chips properly, update the programs and system files.

Have to guess about what applies to "my PC" with no hints at all what it is and what is running, and how slow it is.

Reformat the HDD and install Linux.

Clean out the cache by using the free program called ccleaner.com.

Uninstall unwanted softwares

Keep the storage less