Strangely enough, Java Runtime Environment (JRE) fails to register javaws.exe as the handler for .jnlp files when installed in Windows 8/8.1.

Just remember to choose javaws.exe, not java.exe nor javaw.exe.

Further more, Blackboard Collaborate insists on using 64-bit JRE on 64-bit Windows, i.e. visit the directories and files usually found in C:\Program Files\Java, not the ones found in C:\Program Files (x86)\Java.

BTW, download your clean JRE from http://java.sun.com/ or from http://www.oracle.com/technetwork/java/index.html. On 64-bit Windows it’s usually wise to download and install both 32-bit and 64-bit JRE, i.e. Windows x86 Offline (e.g. jre-8u20-windows-i586.exe) and Windows x64 (e.g. jre-8u20-windows-x64.exe).