Getdataback Portable -

The software is strictly "read-only." It never attempts to "fix" or write to the drive it is scanning. It simply reads the raw data and allows you to copy recovered files to a safe, secondary location.

You can take your USB to any Windows-based machine, plug it in, and start the recovery process immediately.

The software will present various "levels" of the file system it has found. Usually, the top result (indicated by the highest star rating) is the most complete.