Why can't I open my files in OS X Yosemite?

Episode 1147 (1:07:28)

Marilyn from Dana Point, CA
OS X Yosemite

Marilyn has a 4 year old Mac laptop running Yosemite and she's having trouble with her account. She can't open anything. Leo says that's because she needs to update all of her apps now. She says she tried that, but she can't get them to update. Leo says she needs to be an Admin to update software.

The chatroom says that there may be two copies of the software on the hard drive since the app store doesn't update the old version, it just installs a new version. If so, she may not be opening the right version. So Marilyn should remove the old version of the software.