fedora's anaconda installer is very notorious ( and VERY well documented) for not seeing other linux installes on other drives
and / or
setting up grub with the wrong settings for a second or third linux install
it has always been recommended to set then up , in grub.conf, by hand
from the output of
you can get the partition of the DEAD and unsupported( past END OF LIFE ) fedora 11
just off hand WHY do you need the unsupported fedora 11 on the computer along with the current 13
the normal upgrade path is to back up data , reformat ( 13 uses a different default partition format than 11 )
13 uses ext4
11 used ext3
install the current and restore data from the back up .
then repeat EVERY 6 months .