Hi. I had the same problem, and I'm taking the Kaplan course right now. Your problem is your version of Adobe. You need 6.0. Just go to the adobe website (www.adobe.com) and download it, as it's free. You won't be able to download the non-Kaplan tests, but you can get the explanations and the other ones using adobe 6.
Ah, and a hint at downloading Topical Tests- Just download explanations, as it prints the entire test and the explanations with it. It'll save you a little bit of money if you're printing at school.
Other than that, the full-lengths are separate from explanations.
Hope that helps.