I've cleared up some space now in C. I don't think I want to deactive the AV as it's a quite premium version, and I've had it before adding these new parts and everything worked fine then. I can disconnect the VPN to see if there's any difference, but I've also used that before upgrading and it worked well then.The underlying theory of my suggestions was to try and remove things a) not really needed, and b) may be a resource hog.
Your AV for example, removing it is fine. Once removed, Windows will detect that and auto-enable the inbuilt, and excellent, Windows Defender.
Defender has scored as good as any other AV software in independent lab tests for many years now - there hasn't been a need to use 3rd party software for ages, but it is an old habit to break I know!
Same theory with your VPN, it may not be tasking up much or any, but we won;t know for sure until we remove it from the mix.
Show us a screenshot of Task Manager, go to the Details page, click on the CPU column header to sort descending, that'll put the worse offenders up top.
Screen shot that, if System Idle Process is hovering around 98% for the next 30secs or so, you are good to go.
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My Task Manager looks like this when Idle (chrome running),
Yeah I know but I had 2 from before so I bought another pair and tried to keep them somewhat similar. I don't know too much about computers (which is why I'm asking for help), but does altering ram really affect CPU usage?As to the mixed memory - usually not recommended. For starters, it'll find the slowest module and set all the others to that speed. So while you will end up with more memory, you could actually end up with slower memory.
Pick one pair that are the same, and remove those.
Put the remaining equal pair in slots A2 and B2 to get the dual channel benefit.
If no improvement, add the removed pair back.
*Edit, just realized that I didnt include all of the tabs, but the one to the right of the user name is the cpu, and the on to the right of that is memory