The NOOK for PC installer can still be downloaded from B&N's servers
here. I just installed it on Windows 8.1 and signed into my account, so it still works.
If you have a mind to use the
NOOK app for Android on your PC, the
Android-x86 project is a free port of Android to run on PC hardware. It can be installed to a bootable USB drive (I recommend USB 3.0, but I've done it to a 2.0 drive) or it works fine with
VirtualBox as long as you disable "Mouse Integration" from the "Input" menu.
I used to go the VirtualBox route, but I now boot my laptop to Android using a 32GB USB 3.0 flash drive to run the NOOK app. I also use it to play Minecraft with my daughter.