Recently I had an error trying to update Adobe Acrobat and it failed. So I ended up needing to reinstall, then ran into the issue that they don’t tell you the whole product key. (I had the CD but not the case). The whole key is encoded in the registry, but not they don’t show the last 4 digits. After searching for a while I found 2 things that actually gave me the key:
Belarc Advisor (free for personal use) http://www.belarc.com/free_download.html
and a little utility from Dave Hope: http://davehope.co.uk/projects/product-key-finder/
Belarc is a lot to find a simple key. Dave’s utility worked great for what it does.