SD card nightmare

I downloaded a splash (i know, i know - it's a girl thing) and before doing so backed up my stuff.
now i'm getting the big red cross - i have formatted the card and tried to reload my stuff but i stupidly added the splash to my back up (i know!) and now i have taken that out i think some nasty bits have remained as i cant do anything with the card still.... can anyone tell me what files should be in the back up and what i shoudl be getting rid of - i have taken the new splash out and put the old one back in but would there be any residual mess lurking???