help I am stuck with picture package

Up until 2 days ago, when I clicked edit on any of my photos saved in My Pictures files, it would automatically open into Picture Package, from where I could rotate, change colours, compress etc.
Suddenly this has disappeared and I am now opening into a program called Paint which I don't like.
I have tried going into the 'open with' option and scrolling and browsing the list but picture package is not in the program files ...it is in my documents and says folder is empty!!
So have uninstalled and reinstalled it and still the same, so not sure how to re-link it to My Pictures so I can use it as my editing tool.

Any help, in simple language, would be much appreciated as have loads of photos which need editing and filing now.