After upgrading to Win 8.1 with X3c already installed, Addictive Drums step...

I had to open the XLN Installer in order to get Addictive Drums to work again. It was saying I had to enter an authorization code or some thing.
 
I didn't realize this was a program installed on my computer. At first I wasted time hunting through the XLN Audio Website (logging in etc). This got me no where.
 
The solution was to hit the start button and type XLN then open the XLN Installer once Windows found it.
 
Also, with AD, I find that the midi files do not come in as groove clips the way that they did from Session Drummer. I have to click on them and hit ctrl+L to convert them to groove clips before dragging them out.
 
;-)