[CentOS] syslinux and isolinux

Hi

I copied the centos 5.2 x86_64 DVD to a USB pen drive formatted for FAT32.
I then ran syslinux -sf /dev/sdc1 to get it to boot. I mounted it, and did
cp isolinux/vmlinuz .
cp isolinux/isolinux.cfg syslinux.cfg
the setup the  MBR.

THe device booted but I got an error message about unknown command in 
the syslinux.cfg file.

Isnt syslinux and isolinux compatible - they are in the same package?
All these commands below look correct.

Did I do something wrong trying to get a USB pen drive to boot to 
install linux from.

Jerry
----------

default linux
prompt 1
timeout 600
display boot.msg
F1 boot.msg
F2 options.msg
F3 general.msg
F4 param.msg
F5 rescue.msg
label linux
  kernel vmlinuz
  append initrd=initrd.img
label text
  kernel vmlinuz
  append initrd=initrd.img text
label ks
  kernel vmlinuz
  append ks initrd=initrd.img
label local
  localboot 1
label memtest86
  kernel memtest
  append -