From Siam Computer:
S-Ultra Power Spell Checker is a precise and effective spell check software which can be accessed on almost all Windows standard software. It has the additional ability of checking the clipboard for spelling errors as well.
Run Spellcheck in any software
Run Spellcheck on the Clipboard
Built-in Spellcheck feature
Customize the Spellcheck rules to match your specific needs
Create a custom dictionary including your own words
Availability of short-cut keys for greater spellcheck efficiency