Windows 10 Serious Performance Issues

Okay so i know the title is a little vague, but i honestly don't think its just one thing that is wrong with my machine. I've tried everything i can think of but cant get anywhere with it so here i am, i'll describe the problem as best i can.

Im running Windows 10 on my rig, got 8gb RAM, 2TB HHD, 4GHZ AMD processor, GTX 980Ti video card. The computer has seen extensive usage over the past year without any maintenance carried out on it at all, from cleaning out the case to tidying up the system files. I've disassembled, cleaned it, reassembled and hoped to be able to tidy up the system files to restore the computer to working order.

So here is the problem(s):

The computer seems to take a good two, three minutes to boot up, after which it is completely inoperable for another 5 - 10 minutes until it shows a pop up from Microsoft Visual C++ saying "This application hs requested the runtime in an unusual way'. So there is that and the fact that it takes a good, i dunno 20 minutes before i can even use file explorer without it not responding and crashing.

Its really dicy what applications actually work and which don't, some i will try to boot and it'll just seem to be too much for the computer to handle causing it to reset even file explorer.

My Windows toolbar straight up doesn't work, all the shortcut icons have disappeared, the start button, search bar and keyboard shortcuts don't work. So i have no straight forward way of actually doing anything on the system.

I have tried to run an anti virus scan with AVG, but it wont work, so i tried to uninstall AVG and it wont uninstall. So now it seems i don't even have anti virus protection. From there its a mixed bag, somethings can be uninstalled, others cant.

Then i tried to use AVG PC Cleaner to see if it couldn't free up some performance that is clearly being sapped, but it always crashes part way through and never finishes.

Lastly i got tired and decided to just manually back up my steam folder and restore the computer to factory settings, but even doing that doesn't work, it crashes not even halfway through and simply says 'No changes were made'. I don't have a system restore point, so this really was my last option and even that seems to not be able to run on this system.

Im really quite stumped here, i know the information to go off of isn't exactly ideal but has anyone got any ideas?

Have you had any malware on the computer?
Are your files backed up?
Had you made an image of the drive?

This can be approached by troubleshooting one item at a time or you can perform an in place upgrade repair that is is likely to address many issues at one time.
The in place up grade repair is done with a windows 10 iso.
Provided you can complete this in place up grade repair you will be able to keep files and applications.
The in place upgrade repair can be done if you can boot to the desk top, open file explore, and then open a setup.exe file on the bootable windows 10 iso flash drive connected to the computer.
You will need a flash drive that you can format.
To create a bootable windows 10 iso : Download Windows 10
This link will be useful as it has text and images so that you can learn about and perform the in place upgrade repair:
Repair Install Windows 10 with an In-place Upgrade Windows 10 Installation Upgrade Tutorials

If you think you have malware on the computer then you might want to perform a clean install.

AddRAM said:

Why are you using AVG PC Cleaner it`s garbage and you don`t need it.

Do yourself a favor and do a clean install of the Anniversary Update. Especially since you haven`t kept the system in good working order in over a year.

And do yourself another favor and buy a solid state drive to install Windows on instead of that hard drive.

SSD 850 PRO 2.5" SATA III 256GB Memory & Storage - MZ-7KE256BW | Samsung US

If you can afford a 512 GB ssd then get one of them, but it`s not necessary.

SSD 850 PRO 2.5" SATA III 512GB Memory & Storage - MZ-7KE512BW | Samsung US

Clean Install Windows 10 Windows 10 Installation Upgrade Tutorials

I'm aware that i need to upgrade to SSD drives, but those are upgrades, not repairs. I don't have the money to upgrade it at the moment. And like i said in the original post, i cant uninstall AVG OR do a fresh install. Both options don't work for me.