upgrade 4.7 -release

[Hasan Al-rawi]

I am new to freebsd and have installed 4.7 on a couple of laptops, after
trying upgrade from sysinstall i get error when booting saying , no kernel
or kernel.old found. I have used rh8 in the past and upgrading or patching
was straight forward. What do i need to know about patching my freebsd 4.7 ,
are there upgrade methods other than rebuiling the os as i have been
informed?

Hasan