In an odd twist the Lab has made available a legacy Second Life™ viewer for those running obsolete, unsupported operating systems. That means Windows XP and Mac OS 10.7 and earlier. You may know that current releases of the SL Viewer will not install on these older systems.
You can get a copy of this viewer from the Official Alternate Viewers Page. Official name: Second Life Obsolete Platforms Viewer version 18.104.22.1680847.
This viewer will NOT update. There will be no updates and while I am not sure about the auto-update feature I suspect it is disabled.
There is no comment from the Lab about how long it will be usable. The Lab will allow use of the viewer as long as they can. Remember. It is rare for the Lab to block a viewer from the grid that is compatible with the grid. Their only statement is:
This viewer will not get any further bug fixes or new features. It will be allowed for login for as long as reasonably possible.
This is not a solution for those of you that are not updating your operating system for whatever reason. It is a temporary work-around.
I know there are reasons people do upgrade. But, a good used computer with Windows 7 and capable of running SL can be had on eBay for US$200 or less. Plus, Windows 7 users will be getting a free upgrade to Windows 10 in July.