Aspell with Notepad++
Notepad++ is one of my favorite text editors for Windows, but getting the spell checker - GNU Aspell - to work can be slightly tricky.
The key is do not forget to install the dictionary. Both the Windows installer and the pre-compiled dictionaries for Windows are available on the Aspell Windows website. Don’t go to the main Aspll page - they only have the links to the UNIX dictionaries.
After you install Aspell and the English dictionary, you should be able to go to Plugins > Spell Checker, define where the DLL is located, and then you’re ready to start spell checking!