This is a hotfix for the recently released version 4.3 update.
Get the update
- Microsoft Store release
- You can purchase it here. This helps fund development and is an alternative or supplement to sending in a donation.
- If you already have it installed, the update should happen automatically within the next day or two. To get the update immediately, you can follow the instructions listed here.
- Classic Desktop release
- Download the installer directly (web installer for all CPUs and OSes). This is the recommended download if you don’t have Paint.NET installed. It can also be used to update the app.
- If you already have it installed, you should be offered the update automatically within the next week or so, but you can also get it immediately by going to ⚙ Settings -> Updates -> Check Now.
- Offline Installers and Portable ZIPs are available over on GitHub.
Changes since 4.3:
- Fixed an issue with using Explorer’s "Open With" menu on Windows 7, 8.1, and some editions of Windows 10
- Fixed image thumbnails in Explorer’s Details View only having a generic document icon instead of the Paint.NET icon
- Fixed a spurious, harmless error in Settings -> Plugin Errors
- Fixed a race condition that could cause a crash
- Fixed not being able to use Ctrl+C to copy text from the Setup Downloader, which is especially important for troubleshooting
Enjoy!
paint.net blog 
*Fixed an issue with using Explorer’s “Open With” menu on Windows 7, 8.1, and some editions of Windows 10
Still have issue when testing on Windows 10 1909.
In your pre 4.3 you were letting the MSI writing registry keys for Open With menu.
Are you using the MSI directly for deployment? e.g. using /createMsi and whatnot
Could you open a thread on the forum in the Troubleshooting section to discuss this? It’s very hard to have these discussions in the sections comment of the blog https://forums.getpaint.net/forum/3-troubleshooting-bug-reports/
I sometimes get “An I/O Error Occurred when attempting to write the file” in this version.
Log file: https://pastebin.com/ELmBktuc
It says it’s “being used by another process”, but nothing else is using it – my theory is paint.net had some sort of race condition where it was trying to edit and save at the same time?
if there’s any more info I can provide to help, let me know.
Using windows store version