After Lightroom installs, it changes something in Windows so that when I import photos, they go into the LR catalog instead of Pictures. How do I change that setting back? Thanks!
Seems unusual as those options are set by the user when you import images and retained to the next session.
Read all about how to import and set options here: Import photos to Lightroom CC | Adobe Photoshop Lightroom CC tutorials
Photo files cannot go into the LR catalog which is itself a single file - a database, i.e. an index of all your imported-to-LR photos, their names, locations and additional information about them. The catalog file sits in the Lightroom folder inside your Pictures folder. That Lightroom folder also contains a sub-folder (called Lightroom Catalog Previews.lrdata) that contains small preview jpgs that LR makes for its own use. The actual original photo files, however, go by default into the Pictures folder unless you have changed that Destination setting in the upper right corner of the Import page. If you have changed it so the destination is now Pictures/Lightroom, simply change it back to Pictures or to any other destination of your choosing.