![Mac Spell Check Settings Mac Spell Check Settings](http://cdn.osxdaily.com/wp-content/uploads/2011/07/disable-autocorrect-mac.jpg)
Reset for Single Document. Open a document in Word and enable Spelling and Grammar check on the document by clicking “Review” in the top navigation ribbon, and then clicking the “Spelling & Grammar” tab. Change or ignore misspelled words, as desired, when the Spelling dialog box displays a suspected misspelling. Spell check the entire document.
If you are just annoyed by the feature, you can disable it in Preferences - Spelling by unchecking the box for Check spelling as you type: You can re-enable it after you're done working with this document. If you need to keep English spell check, double-check your system language setting in System Preferences - Language & Text - Language.
I doubt this has changed without you noticing, but there's an off chance PowerPoint may be taking its cue from this setting. I've always had issues with multiple languages in Microsoft Office, so during installation, I disable all languages except for English.
This would be a surefire solution if you don't need the extra languages, but it would require you to uninstall and reinstall Office. Finally, I would strongly encourage you to look into ($20 through the App Store) as an alternative to PowerPoint. There would be a bit of a learning curve while you get used to it, but it's quite powerful, the interface is sleek, it runs perfectly, and I find that it's easier to make things 'look nice' in Keynote than in PowerPoint. University classrooms will have a video hookup that you can use to run your presentation from a Mac laptop, but if it's not an option for you to run your presentations from your Mac, it can export PowerPoint-compatible files pretty well.
You're not struggling with a Microsoft operating system, so why struggle with Microsoft software? Simplest answer / your language tool has defaulted to a language you do not want it to be. Go into TOOLS menu,. Select Language., You will see your list where you have all the standards including Basque, Catalan and Spanish (Castellano) etc. Make your choice and select default. You have now changed your function of spelling for all documents.
Use this facility to check specific text by first selecting your text and then select the language just don't select default. This way you can check just a word, a sentence or a whole document easily as advise by a couple of the posts above.