Does Powerpoint 2003 work with Keynote
Unfortunately, Keynote and Powerpoint do not talk to each other all that well. A lot of formatting issues have been known to occur. 

If you're wanting to view/edit/present the presentation on your iPad, I would suggest using Keynote on your Mac and Keynote on your iPad. If you're wanting to stay as compatible with a Windows environment as possible, I would suggest using QuickOffice HD on the iPad and Microsoft Office for Mac 2011. 

Hope this helps.