Recently, I did a reinstall of Window 10 on my main workstation. As I was reinstalling software I took note of some of the useful and mostly free tools I use.

Screenpresso

"Time saver for explaining something to your colleagues and clients."

Image and video screen capture software. There is a free version and paid version. Pro version adds a few features and the free version will do 90% of what most people will need from the program. There are other screen capture programs available and I always come back to screenpresso.

https://www.screenpresso.com

Mostly Free.

F.lux

"Software to make your life better."

F.lux adapts the color of your computer's display to the time of day making it warm at night and like sunlight during the day. You may be thinking, "Can software that changes the color temperature of my computer display actually make my life better?"

Yes, it can.

https://justgetflux.com

Completely Free.

Keypirinha

"A fast launcher for keyboard ninjas on Windows"

I almost hesitated putting Keypirinha on this list, because it is a really "big" program and the configuration is a bit complicated (you have to edit text files). I use less than 1% of Keypirinha's functionality and what I do use is responsible for about 90% of my productivity. How could I not include this?

https://keypirinha.com/

Completely Free

Microsoft PowerToys for Windows 10

"A set of utilities for power users to tune and streamline their Windows experience for greater productivity."

I only FancyZones and PowerRename. I disable PowerToys Run because it duplicates Keypirinha's functionality. FancyZones is a must have if you have multiple monitors. PowerRenamer is the most convenient bulk RegEx file renaming tool I have found for Windows 10.

microsoft/PowerToys
Windows system utilities to maximize productivity. Contribute to microsoft/PowerToys development by creating an account on GitHub.

Completely Free

VeraCrypt

"VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux."

If you want to keep your data private, then use VeraCrypt.

VeraCrypt - Free Open source disk encryption with strong security for the Paranoid
VeraCrypt is free open-source disk encryption software for Windows, Mac OS X and Linux. In case an attacker forces you to reveal the password, VeraCrypt provides plausible deniability. In contrast to file encryption, data encryption performed by VeraCrypt is real-time (on-the-fly), automatic, transp…

Completely Free.

7-zip

"A file archiver with a high compression ratio."

Windows can uncompress .zip files, this is easy and convenient. When the built-in Windows functionality falls short 7-zip picks up. It does everything else you need a file archiver to do. Small and fast.

https://www.7-zip.org/

Completely Free.

WinSCP

"Free SFTP, SCP, S3 and FTP client for Windows"

The tag line from the website pretty much says it all. Simple, easy to use integrates with Putty. If you do not know what Putty is, don't worry about it.

WinSCP
WinSCP is a popular free SFTP and FTP client for Windows, a powerful file manager that will improve your productivity. It supports also Amazon S3, FTPS, SCP and WebDAV protocols. Power users can automate WinSCP using .NET assembly.

Completely Free.