520: see what is on my SD card and play downloads

[Elizx]

Lumia 520: I used HD Tube-Best Client to download videos from YouTube, stored them on my SD card. The app no longer works and I can't find it in the Store to refresh it. It think it has disappeared. How do I (1) see my videos on the SD card (2) play them.

I have another YT app - Touch Tube, and that is still working (for the time being...).

Any suggestions greatly appreciated.