I wrote about a problem with the viewer repeatedly downloading updates. The cause is the shortcut a person uses to start the viewer. Initially it was the folder name that changed and threw off the shortcut. Now my recent update to 3.6.13 went into an update loop.
It seems the SL Viewer program in 3.6.11 was named SecondLife.exe. The new 3.6.13 program is named: SecondLifeViewer.exe. So, if you have a shortcut pinned to your desktop, you will probably need to change it again. Just unpin it.
The viewer update or install will create a new shortcut on your desktop. That new shortcut can be pinned to you task bar via right-click drag and drop.
You can also find a shortcut in the Second Life folder in: Programs Files (x86)/SecondLifeViewer. That can be dragged to the task bar and pinned too.