Paint.net is free!

About
Paint.NET is free image and photo editing software for PCs that run Windows. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. An active and growing online community provides friendly help, tutorials, and plugins.
It started development as an undergraduate college senior design project mentored by Microsoft, and is currently being maintained by some of the alumni that originally worked on it. Originally intended as a free replacement for the Microsoft Paint software that comes with Windows, it has grown into a powerful yet simple image and photo editor tool. It has been compared to other digital photo editing software packages such as Adobe® Photoshop®, Corel® Paint Shop Pro®, Microsoft Photo Editor, and The GIMP.

About
Paint.NET is free image and photo editing software for PCs that run Windows. It features an intuitive and innovative user interface with support for layers, unlimited undo, special effects, and a wide variety of useful and powerful tools. An active and growing online community provides friendly help, tutorials, and plugins.
It started development as an undergraduate college senior design project mentored by Microsoft, and is currently being maintained by some of the alumni that originally worked on it. Originally intended as a free replacement for the Microsoft Paint software that comes with Windows, it has grown into a powerful yet simple image and photo editor tool. It has been compared to other digital photo editing software packages such as Adobe® Photoshop®, Corel® Paint Shop Pro®, Microsoft Photo Editor, and The GIMP.
Paint.NET - Downloadpaint.net 4.0.12 is now available
This is a hotfix for some crashing on single CPU systems, and a rendering bug in the Rounded Rectangle shape.
As usual, you can download the update directly from the website, or you can use the built-in updater via Settings –> Updates –> Check Now.
Change log:
And, for convenience, here is the change log for 4.0.11:
- Fixed: Rounded Rectangle rendering was incorrect for some values of "Corner size"
- Fixed: Effects and Adjustments were crashing the app on systems with only 1 CPU core, or virtual machines configured for only 1 CPU
Enjoy!
- New: Rounded Rectangle’s corner size ("radius") is now configurable
- New: Overscroll can now be disabled from within Settings
- Fixed: The Zoom tool was broken in 4.0.10
- Fixed: Auto scroll will no longer engage overscroll. This prevents the image from shooting off in all directions when drawing on it or when making a selection.
- Fixed: Panning with the middle mouse button would sometimes be "sticky", as reported at Dragging with the mouse wheel is "sticky"
- Fixed: Effect rendering performance had significantly regressed in 4.0.10, by as much as 50%, on Intel CPUs with HyperThreading.Paint.NET run significantly slower on Windows 10 compared to Windows 7.
- Fixed: Selecting the entire image and then using Zoom to Selection or the Zoom Tool would align the image in an awkward manner
- Fixed: In rare cases, Settings -> Plugin Errors was hanging the whole system (bug in WPF?). This UI is now implemented in WinForms instead of WPF.Plugin Error screen = Complete PC Freeze/Lockout
- Fixed some more high-DPI issues, especially when using multiple monitors with mixed DPI, or when using Remote Desktop