We did this promotion last year and it was a hit, from the website:

For a limited time, you can get a free, second shot at any IT professional, developer, or Microsoft Dynamics certification exam. Just register for this offer before your first exam, and you will get two chances to pass. But this offer won't last forever.

http://www.microsoft.com/learning/mcp/offers/secondshot/default.mspx

Takes the worry out of testing, so nows your chance to get those certification exams done that you keep putting off!!!!!