Problems with .tar file

["Jose Luis Guerra" <guerra@mad.azkar.es>]

    Hello, I write from Spain and I'm novice in Linux World.

    I have a problem processing  .tar file. When I write command "tar
xvf <file>.tar" to extract the file qt-1_42_tar.tar, then computer
return then next error message:

        tar: Hmm, this doesn`t look like a tar file
        tar: Skipping to next file header
        tar: Skipping to next file header
        tar: Only read 1285 bytes from archive qt-1_42_tar.tar
        tar: Error is not recoverable: exiting now

    Please help me and sorry by my bad English. Regards