As this is a tablet rather than an eReader there may be another way.
Try intalling the Bluefire app on the tablet.
http://www.bluefirereader.com/bluefire-reader.html
You should be able to register your Adobe ID with that,
and buy and download books directly without using the PC or ADE at all.
I have not done this myself, just used Bluefire on an iPad as a reader, but it claims it should work.
I still can't think of any reason that neither version of ADE will work on your Windows 8.