I bet it's how you saved it, or how the browser saved it. You might have to:
Code:
mv kernel-source-2.4.20-noarch-5.tgz.tar kernel-source-2.4.20-noarch-5.tgz
then from there run
Code:
installpkg kernel-source-2.4.20-noarch-5.tgz
or
upgradepkg kernel-source-2.4.20-noarch-5.tgz