This is probably a .tar.gz or a .tar.bz2 file that has had its file extension mangled by Microsoft Internet Explorer, in order to match the MIME type of the file.
Back to Linux, use
to find out if you have a bzip2 (.bz2) or gzip (.gz) compressed file. Then correct the filename
mv file.tar.tar file.tar.bz2 or gz
and then go as normal.
Alternatively, it could be a tar file contained inside another tar file (a rather pointless thing to do, but possible). In which case, untar it to extract the [b].tar[b] file, then untar that as normal.