I tried to do a reinstall. And got this. besinstall.jpg
The box that is half-covered says "backup the existing db before installing"
I could uncheck that, and then just copy the mdl and ldf files back later, IN THEORY. But the last time I tried that I was getting all sorts of errors, which I am sure were caused by try to go from one version of BES to another. But I still ended up having to reactivate all of the blackberries.