Windows updated and now when I try to open Lightroom it gives me a message that says "Lightroom encountered an error when reading it's preview cache and will try again when restarted" Restarting it does no good at all.
The problem you are experiencing is not related to a Windows update. The preview cache has become corrupted. You need to use Windows Explorer or Finder to open the folder that contains your catalog. Locate the folder that has the extension .lrdata and delete that entire folder. Then start Lightroom as you normally do. Lightroom will be in building a new preview folder and you should be able to continue normally.
I don't know the reason, but quite a few people have experienced this same issue. Take a look at the "more like this" list to the right of this message. It is more common than you might expect.
Thanks so much I did what you said and it worked like a charm!