How to Add Words to the Dictionary in PowerPoint 2007
The PowerPoint spell checker uses the standard dictionary. If you have some unusual words or alternative spellings in your PowerPoint presentation, PowerPoint will mark them as errors. You can add them to the dictionary by clicking the Add button when the spell checker finds a spelling error.
Dictionaries are shared by other Microsoft programs, such as Word, that use spell checkers. So if you add a word to a dictionary in Word, the PowerPoint spell checker knows about the word, too.
If you are working in a custom dictionary and accidentally add a word to the dictionary, you can edit the Custom.dic file. The easiest way to edit the Custom.dic file is to choose PowerPoint Options from the Office button, click Proofing, and then click the Custom Dictionaries button. You can then select the Custom.dic file and click Edit Word List to edit its contents.