I have been sloppy with my OPSEC since I started using DNMs 9 months ago and I have sensitive data that could be used to incriminate me in my computer (DNM passwords and photos). I do not trust the encryption tool provided by Windows, which software should I use instead?
You shouldn't use windows to open sensitive files.
Use the disk encryption that comes out of the box with your favorite linux distribution in a usb stick and a secure password.