The one way to upgrade Fedora is by using Yum and 'preupgrade'
Try this instructional page. It should work-
How to use PreUpgrade
If that doesn't work you may have to download a fresh ISO Image of Fedora 17 to DVD/CD or USB-
About the default installation script; I found this:
About the Default ks.cfg Installation Script
The ESXi installer includes a default installation script that performs a standard installation to the first detected disk.
The default ks.cfg installation script is located in the initial RAM disk at /etc/vmware/weasel/ks.cfg. You can specify the location of the default ks.cfg file with the ks=file://etc/vmware/weasel/ks.cfg boot option. See Enter Boot Options to Start an Installation or Upgrade Script.
When you install ESXi using the ks.cfg script, the default root password is mypassword.
You cannot modify the default script on the installation media. After the installation, you can log in to the ESXi host and use the vSphere Client to modify the default settings.
The default script contains the following commands:
# Sample scripted installation file
# Accept the VMware End User License Agreement
# Set the root password for the DCUI and Tech Support Mode
# Install on the first local disk available on machine
install --firstdisk --overwritevmfs
# Set the network to DHCP on the first network adapter
network --bootproto=dhcp --device=vmnic0
# A sample post-install script
%post --interpreter=python --ignorefailure=true
stampFile = open('/finished.stamp', mode='w')
stampFile.write( time.asctime() )
Hope this helps