I am surprised that there isn't an "Office-wide" setting for disabling spell checking and grammar checking but apparently there isn't. Hopefully with the drive towards making Office a "system", the next version will have some generic options that apply across all programs more than just the few that are available now in Office 2007.
With that said, if you are curious how to disable spelling checking and grammar checking in:
OneNote 200x, Outlook 200x, PowerPoint 200x, Publisher 200x, Word 200x, Visio 200x, InfoPath 200x, and SharePoint Designer 200x, read about it
here.