You can import Microsoft PowerPoint 2010 slides into an Adobe Captivate 5 project. During the import, Adobe Captivate automatically converts the slides from .pptx to .ppt format (if a converter is available, or if PPT 2007/2010 is available).
However, Adobe Captivate 5 has not been thoroughly tested with Microsoft PowerPoint 2010. Some functionalities of MS PPT 2010 may not work as expected in Adobe Captivate.
Best practice: Create a backup of the MS PPT 2010 project before importing it into Adobe Captivate or while importing, uncheck the 'Linked' option in the Convert PowerPoint Presentations dialog box. By doing so, you retain a 'good' copy of the source just in case the Adobe Captivate project gets corrupted due to unsupported functionalities.