Don’t have Photoshop and need to open PSD files? Are alternatives like GIMP too slow and heavy? I recommend Paint.NET as a great free alternative to Photoshop because its lightweight and fast. Unfortunately, it does not support PSD files. Luckily, thanks to a free plugin, it can open and save PSD files.
Simpy download the zip file and extract Photoshop.dll. Place this file into the FileTypes directory inside your Paint.NET install directory. Then, just open up Paint.NET and PSD files can be opened and saved.

The Photoshop Plugin adds an option to save and open PSD files
Not all Photoshop file features are supported however in my testing, this worked quite well as a great lightweight alternative to Photoshop. According to the plugin site, the following features are supported:
Layers Masks (only loading see To do list) RAW or RLE compressed files The following color modes are supported for loading an image
Gray scale Indexed 32 Bit-RGBA CMYK (lossy conversation) Multichannel CMY (lossy conversation) Duotone (as gray scale) Lab (lossy conversation) For saving an image only 32-Bit RGBA is supported
Download Paint.NET here (Windows only)