kernel-2.4.20-13.9.src.rpm is the source rpm,
the rpm used to rebuild the kernel.
You must download
the rpm with source kernel.
And by the way don't remove manually
files installed with rpm.
You should use
rpm -e kernel-source
to do a clean package removal.
I think you have to use
rpm -U kernel-source-2.4.20-13.9.i386.rpm
to install the new package.