May be VIRUS, Reinstall photoshop. Or

Program -> Accessories -> SystemTools -> System Restore

It will work only if you already set a storage point on some other previous dates.

Yes it is virus. You clean width a virus program. and restore the photoshop or reinstall.

What exactly are you saying?

1. You were working on a file in photoshop when everything shut down and the only version of the file you have is .jpg and not .psd?

if so, there will be nothing you can do about that. You will need to redo whatever you had done in photoshop before the shutdown. This is a great learning lesson to save often. It's fast and easy. ctrl + S.

2. When you are working with photoshop the only option for saving pictures in is .jpg?

How are you trying to save images? File-->Save for web & devices or file-->Save As?

there is two option
1. you can save your work frequently
2. Reinstall photoshop