Help! When I double click on a folder, it defaults to SEARCH instead of OPEN!

I got home from work tonight and booted up. Magically (unless I'm an idiot and can't remember doing something stupid), when I double click on a folder or on a drive, the search window comes up instead of opening the folder. It's driving me crazy!

Also, when I right-click on a folder or drive, the menu that comes up has "Search..." in bold letters as the first (and I'm assuming default) item, instead of the usual "Open."

How do I change it back to open?