Microsoft PowerToys is a fantastic program if you like to tweak your experience with Windows.
It lets you do things like set up individual zones within your monitor that act like picture in picture or another monitor. It has a robust color picker, which helps greatly when it comes to photoshop and template creation. I also use the text extractor very often to extract text from pictures, which it copies to the clipboard.
The best, and technically the worst, is it lets you change settings that you can't normally do in Windows.
While it could get someone YOLO adminning in trouble, thankfully it has a lot of warnings before you mess things up too badly.
While not a "Windows program," Ninite allows you to queue up and download a lot of the most common software installs you'd make after a fresh install.
In terms of actual windows programs, I quite like "Everything." It's basically a database of all the files on your computer that allows for near instant searching.
"Space Sniffer" is an excellent utility for finding what takes up a lot of room on your drive.
"Unidentified flying raw" is a free program that allows the manipulation and conversion of raw picture files. I use it before editing in Gimp, but if you have Photoshop, it's not necessary.
"Dark Table" is an acceptable free light room alternative if you have the patience. It's pretty slow though.
VoidTools' Everything. Indexes your whole filesystem (across all drives too) and allows you to search your whole filesystem for matching filenames, save search presets for later, and even allowing RegEx search queries if you need files of names matching some pattern.
I am an IT guy, as a general rule I don't install stuff I don't need.
That being said, we all have different requirenments for our computers, and I would be dumb to enforce my requirenments on you.
So here are some great tools and utillities that I have used and in some cases still use.
Firefox - Google Chrome needs a rival to keep the web happy, it is an excellent browser and have served me well for 20+ years.
VLC - Video Lan Client, I have yet to find a media file that this player can't play, this is less relevant since piracy have gone down, but I still keep in on my system.
digiKam - A photo organizer, works well with all formats I have thrown at it, currently manages my growing collection of photos (see my profile for a photo I took of a Lynx Kitten), it also makes me able to do light photo editing, but I mainly use Affinity Photo for that.
Strawberry Music Player - An advanced music player, based on Clementine Music Player which is based on amaroK musik player. It gives me a great album interface to managemy music, less usefull now since I buy most of my music through iTunes, but still does an excellent job of managing growing collection och C64/Amiga remixes from remix64.com
Notepad++ - This should be on every windows computer, it is an advanced text editor, it has everything you need from a text editor, plays way more. It is fast, has persistant tabs, syntax highlighting, autocomplete, themes and way more.
VS Code - Visual Studio Code, this is a source code editor, it is like taking Notepad++, making it snort cocaine and bolting a modern interface to it. This is not a general text editor, this is a program where you write and edit code, Notepad++ is excellent for reading and making quick changes to text files, VS Code is what you use to develop the code. It assists you constantly, from autocomplete, to error checking your code, I write a lot of Powershell code in VS Code at work, and it is great. It is slower to get going than Notepad++, but once you start it and have it co figured it works great.
Gimp - The Gnu Image Manipulation Program, free but less refined version of Adobe Photoshop, it is highly capable.
Libre Office, a less refined version of the office suite.
You can use it to flash an ISO for a free operating system instead Microsoft Windows spyware. You could go Linux, or BSD, or Haiku, or whatever so long as your personal data & freedom are respected.
If you're still using Windows 10 you should try out Powertools by Microsoft. It adds a lot of quality of life improvements, like adding a grid to snap your windows
AutoHotkey - one of the best GUI automation and scripting tools for Windows. You could create anything from a simple key-ramapping macro to full fledged, standalone apps - it's super easy, yet super powerful. Highly recommend checking out if you ever wanted to automate something, or you wanna make your own app for whatever, but you don't wanna learn a complicated programming language.
NAPS2 (Not Another PDF Scanner) does exactly one thing, scan stuff, and it does it incredibly well. Bypass all the garbage software that came with your scanner, plus it supports batch processing and profiles.
It's practically a necessity if you use a metered or paid internet connection, or connect your laptop to a cell phone for an internet connection via a hotspot.
Windows doesn't listen to its own settings about metered connections and if it deems something worthy of killing your data plan for the month, it'll do so without your knowledge.
The best part is that when you're ready to download critical updates or something from the Windows store (Whatsapp, Minecraft, Power Tools, etc.) then it's as simple as a button press to reactivate updates without restart.
If I would have been asked to choose one really useful piece of software on Windows it would be Agent Ransack. I use it to find strings in a bunch of files, even compressed ones. I believe it can do much more but I use it for this purpose on daily basis. There's a paid version but the light one is free and does all I need. https://www.mythicsoft.com/agentransack/
A lot of great free and open source software works with windows. Librewolf web browser, kdenlive video editor, Gnu Image Manipulation Program (GIMP), Freetube is a great YouTube front end. Youtube-dlp is an excellent command line tool for downloading videos and music locally from lots of websites not just youtube
For games freedoom, super tux, minetest with the mineclone2 game installed,