Hmm... no main package?
This is what atleast I can see at
ftp://ftp.suse.com/pub/suse/i386/9.1/suse/i586/
yast2-2.9.60-5.i586.rpm
yast2-bootloader-2.9.22-1.i586.rpm
yast2-control-center-2.9.11-3.i586.rpm
yast2-core-2.9.79-3.i586.rpm
yast2-core-devel-2.9.79-3.i586.rpm
yast2-country-2.9.19-9.i586.rpm
yast2-debugger-2.9.2-11.i586.rpm
yast2-devel-2.9.60-5.i586.rpm
yast2-ldap-2.9.10-10.i586.rpm
yast2-mouse-2.9.10-10.i586.rpm
yast2-ncurses-2.9.20-3.i586.rpm
yast2-network-2.9.32-1.i586.rpm
yast2-nis-client-2.9.15-11.i586.rpm
yast2-online-update-2.9.11-3.i586.rpm
yast2-packagemanager-2.9.37-0.i586.rpm
yast2-packagemanager-devel-2.9.37-0.i586.rpm
yast2-packager-2.9.43-3.i586.rpm
yast2-pam-2.9.10-9.i586.rpm
yast2-perl-bindings-2.9.25-8.i586.rpm
yast2-printer-2.9.23-1.i586.rpm
yast2-profile-manager-2.9.7-11.i586.rpm
yast2-qt-2.9.21-0.i586.rpm
yast2-slp-2.9.9-2.i586.rpm
yast2-sound-2.9.19-4.i586.rpm
yast2-storage-2.9.37-0.i586.rpm
yast2-transfer-2.9.2-10.i586.rpm
yast2-tune-2.9.20-10.i586.rpm
yast2-update-2.9.23-2.i586.rpm
yast2-users-2.9.27-1.i586.rpm
yast2-x11-2.9.9-10.i586.rpm
yast2-xml-2.9.8-10.i586.rpm
As you can see there is really many yast-modules to be downloaded.
But since 9.1 is so old that it doesn't have support anymore I would recommend updating to a newer version. Suse 9.3 or Suse 10.0 maybe.