What did I do?????????

I finally have found my external hard drive that I store my pictures on!! Well, earlier I started moving the pictures over that I did not have on my external. I backed them up on DVD's too!! So, I go and delete them from my puter. I open up Picasa try to export some pics for a project I am working on and can not export them! I keep getting a message about read only files! So, I reodo my picasa only to loose stuff, then i uninstall redownload and well I have no clue where that file just went! SO now I am REDOWNLOADING it agian!! What did I do??????????