This problem has been discussed before. I searched the forum but can not find solution.  I hope this will be useful for those beginning using linux.
The error during install seadas 5.0.3 on Fedora 4 is:
/seadas5.0/idl_rt/bin/bin.linux.x86/idl: error while loading shared libr aries: libXp.so.6: cannot open shared object file: No such file or directory

I download the RPM resource libXp.so.6 from this website for Fedora 4 i386.
http://rpmfind.net/linux/rpm2html/search.php?query=libXp.so.6

I save the rpm file to a directory /home/An/Desktop/.
In a terminal, run:
su -
rpm -ivh /home/An/Desktop/xorg-x11-deprecated-libs-6.8.2-31.i386.rpm

That's it