If you are more concerned with preserving your presentation’s layout and text and image quality, then the following procedure is the fastest and easiest way to convert Keynote to PowerPoint:

1. Export from Keynote to PDF.
2. Open the PDF in Adobe Acrobat Pro and select Document > Extract pages, and make sure that the page range is for all pages and that the box for ‘individual files’ is checked. This will convert the single PDF into a PDF file for each of its pages.
3. Create a new, empty Keynote presentation.
4. Drag the extracted PDFs into the empty Keynote presentation’s ‘Slides’ area. This will import the PDFs into the presentation, one slide per file. For some reason, you can’t do this in PowerPoint.
5. Export the new Keynote presentation to PowerPoint. You can now delete the new Keynote presentation.