I promise this is a genuine question and not a Windows hit piece.

Every Windows computer I've ever had has slowly gotten laggier over time until my impatience has forced me to reinstall the OS to get the speed boost that comes with a fresh copy. In the schools I've worked in, computer labs and carts full of Windows machines have slowly sunsetted, becoming wholly unusable over time. I think Chromebooks have taken over education in part because they have a snappiness to them that sticks around for a long time, unlike the decay demonstrated by Windows computers.

In my current job, I was issued a Windows computer and a Chromebook at the same time, when I was hired. The Chromebook is still chugging along just fine, but the once fresh and quick Windows computer is now ramping down. I know it's not because of startup or background programs latching on over time because I don't have admin rights and thus can't install anything! I'm not a power user either. I really only ever run a browser with minimal tabs, along with the very occasional instance of office software and/or PDF reader. That's it. And what used to be instant and quick is now like... trudging... through... sludge...

Is there some fundamental design flaw in Windows? Am I finding a pattern where none exists? Do I not have enough experience with other OSes to know that this is true for them too? I'd love someone's insight on this topic.

What are some of the must-dos, must-installs, must-uninstalls, and must-alters of setting up a new PC? I'm getting my first new PC in 5 years on Sunday and the old one is really showing its age. I would like to avoid that as much as possible in order to keep the PC running smoothly as long as possible. I'd also like to optimize its performance and have useful software tools.

Thank you for any advice,
gbbb

I'm not sure if this is the right place for this, so please let me know if I should post this to a different group instead.

I have 3 drives on my current PC, but the C: drive is almost full (it keeps bouncing around between 2-1 GB left) and it seems to be slowing some programs down. Most noticeably Audacity stores temporary files in C: while I am working on large files and it often changes wait times on an edit to upwards of 30 seconds (meaning literally nothing happens for 15-45 seconds and then the change takes place, even if it's only a simple few second deletion).

Is there a way to set my D: or E: drive as the default drive of the computer so I can clear out some space on my C: drive and use the extra space I have on those drives? Thanks for any help or information you can give me.

Oddly all off a sudden, while I was watching a video, my phone started to play the same sound as my PC speakers. It was kinda of cool, like my phone was a second speaker. But it did it automatically. Anyone else see this? I have access to YouTube music now so maybe that's a new feature or something?

edit: My device is Windows 10 PC using regular Chrome and Google Pixel XL (Android P)