Could having LARGE amount of small files on your HDD Slow down the pc ?

Reserved for Gibs.

Yes.

yes

So, you have only one drive with no partitions?

Is it a standard drive or SSD? If its pretty full, more than 70-80%. It can definitely cause slow downs. Also depending on where its stored, like a desktop. The desktop on most OSs is set to keep it constantly ready. So the less you can have your desktop, at least file wise, will help. Shortcuts and the sorts are fine.

EDIT: Sorry for the technical question. I work in a small repair shop for computers and servers.

Delete all those lolipics

I suggest you do what my friend does. Get an external HDD for that storage.

Yes they can. Even one large file can slower down more then many little files, if he fragmented (splitted) on many little clasters on all over partition.
Tried to clean up and use defragmentator?

If it's an SSD, no. If it's an HDD, yes.

Think of an HDD like a giant library, and the files not as books but as pages. A file consist of multiple pages of varying amounts, and the pages can be spread over multiple books. So in order to get a file, it has to open multiple books spread around the library, and get the required pages from each book. Sometimes a book suddenly becomes smaller because something was deleted, so there is once again space to shove in some pages, next time something needs to be written (saved) and it fits in the book, it will shove it in that book (first available space).

The more books there are, the bigger the mess, the slower the processing of files.

It's not 100% accurate in technical terms, and there are ways to optimise it even with that many files (Defragmentation, indexing, etc etc), but it should get the point across. The fuller a drive is, the more work the HDD has to do to get what you want. Like an overworked librarian.

Yes it could slow it down, especially if the files share the same drive as your Windows.

Try a defrag with Glary Utilities perhaps. Run the Windows Disk Cleanup as well, see how much the thumbnails file is taking up. Also, keep the folder(s) somewhere other than your desktop as someone else mentioned so that it is not constantly being accessed.

download and install advanced system care 10.3 (startup optimization, registry clean and defrag, vurnerability fix, disk scan, disk optimization, system optimization, etc)

simple answer: yes
avoid too much, use vhd if possible

The more you have in your hard drive does NOT affect speed.
How fragmented what you have in your hard drive is? DOES effect speed.
So if you have a lot of smile files cutting up your game installs, THAT could cause some slowdowns in loading and etc.
You can have as much downloaded as you want assuming it's not fragmented without it affecting speed UNLESS you are trying to run a lot of it at once. That's the exception. Because then your disk needs to access more at once, obviously.

it kinda happens based on wat windows you have, windows 10 have some index active on the main system, w8 or 7 doenst most of time, you can also forxe the index on the sytem files, and course take a look at your virtual memory, sometimes ppl set a ridiculous number becase hey 1tb! but if the files invade the vm then your system will fail, also some hds show their teoubles if you suddenly fill 90% or more of it, in special disc drives, ssd's dont show this so much.
Try check the index, remake it, do a defrag and maybe a scan for troubles on the hdd, it should help.

try to arhive this files without compression, if its a problem with a large amount small files - this may help (but you need a large amount of free space)
also mb windows indexing this files, if you have this option enabled - that may slow down pc

Yes.

Yes, it's happen to my you-know-what-weebs-collect video
got too much of it and it slows down
after some auslogic optimize defrag and some file managing it's getting kinda faster

Run Auslogics Disk Defrag, in settings/alogrythms set Move System files and Optimize by prefetch, in Disk Cleanup check everything.
Now run the defrag in Defrag and Optimize. It'll take a good few hours, but it will speed up disk access.
All the Standby Memory use makes me think you have photo or movie player loading on startup, therefor filling up your ram in case you want to watch something. Check all your startup items and disable all but the essentials to run, then give it a try. You should find the culprit program by testing each item re-enabled one at a boot.
Good luck :)

Your whole PC?
Not necessarily.

Did using Disk Defragmenter helps?

I got a couple of hundred thousands of files and was going to say it's fine (better to turn windows index off though!) till i read 3 million..

Malware and virus is a distinction, if Malwarebytes says you are clean, doesn't mean you couldn't have a virus, why i still use both Malwarebytes and something like Eset, and even the best can sometimes miss something (especially when it's new) some will say only a good Antivirus Suite is enough, and they do go better in getting malware too these days.

There is just alot that can result to thing slowing down aside from a full hd, but you already been given things to work with.

Also, defrag.