Hi haphomem, can you tell me a bit more about the files you saved on your USB drive - are those files (personally-made lessons) saved or exported from Little Reader?
The "files have been damaged" error usually appears when you try to open a file which was not downloaded completely, or if the file is corrupted.
As an initial solution, please follow the instructions here to re-download and install Little Reader from your account page:
http://support.brillkids.com/entries/20370881-Installing-and-Setting-Up-Your-Little-Reader-from-your-BrillKids-Account-If you didn't create any personal lessons before your laptop broke down, you don't need to use the files from your USB anymore. As soon as you finish installing Little Reader (as per instructions from the link above), you can start playing the lessons again.
Otherwise if your USB included personally-made lessons, try to copy the files from the USB onto your desktop (or any location in your computer), then open the files from there instead of opening the files directly from the USB.
I hope this helps!