Spell check is not installed on Windows Notepad++ by default so to make it work you actually have to install a third party application called Aspell. To check and see if Aspell is installed on your Notepad++ version simply open a new document, write a sentence, and then click the spell check button which is shown in the image below.
The button is located on the far right side of the row of buttons above the tabs and has ABC and a check mark located on the button. When highlighted the text “Spell Checker…” will appear below the button as shown in the image above.
Notepad++ Spell Check Error:
When you click the button it will pop open a “How to Use Spell-Checker” window if Aspell is not installed as shown in the below image.
To get Spell Check working on your Windows XP computer running Notepad++ simply follow the directions in a previous Question-Defense.com article located here. The basics are installing Aspell followed by a installing precompiled dictionary which in my case was Aspell English precompiled dictionary. After these have been installed and Notepad++ restarted the Aspell spell check will work as shown in the below image once the spell check button has been pushed.
Notepad++ Aspell Spell Check Working:
There will more than likely be many words that are not included in the English precompiled dictionary however you can expand the list of words included in your dictionary by clicking the Learn button on words that are not included. In the above image the precompiled dictionary does not include XP so once verified that XP is spelled correctly click the Learn button and XP will no longer be required to be modified when you run Notepad++’s spell check.