dell R710 on ESXi 4.1 upgrading to 5.1 error

I downloaded the dell customized esxi 5.1 recovery CD from 

http://www.dell.com/support/drivers/us/en/19/driverdetails?driverid=XWYR5

but when i try to upgrade my esxi 4.1 server it give an error about vibs not available on the iso.

any idea?

I am using a kickstart script with upgrade command

upgrade --firstdisk=local