So I fired up one of my Seagate external backup drives and I couldn't access a folder. That was a folder with about 92 GB of files in it. Eek!
From within Windows Explorer Right Click on Drive and select Properties. Tools Tab, Check Now, check mark Automatically Fix File System Errors Took a long time (500 GB drive). I almost thought is wasn't working. But fixed it. Yay! Whew!
I think that's equal to chkdsk drive: /f switch. I tried to just scan for errors but got a popup error and it would not work. One of those moments I was ever so glad I had double backup drives.