Have you tried this alternative method? http://wiki.centos.org/HowTos/InstallFromUSBkey

The unetbootin technique may be suffering from an Anaconda bug: https://bugzilla.redhat.com/show_bug.cgi?id=568343


On 26 Nov 2010, at 1134, Werf, C.G. van der (Carel) wrote:

> Hi,
>  
> I’m trying to get Scientific Linux 5.5 installed from USB-key, since my system does not have a working DVD player.
> I used “unetbootin” and “SL.55.051810.DVD.i386.disc1.iso” to create a bootable key. The tool extracts the installer files from the ISO to the key.
>  
> Booting the key the SL5.5 setup program keeps looking for an “.ISO” file, in stead of looking at the extracted files on the key.
>  
> How can I pinpoint the installer to look at the key ?
>  
> PS. Since the ISO-file is over 4 GB it can not be copied on the FAT32-usb-key !
>  
>  
> With Regards,
>  
> | Carel van der Werf | Developer/Administrator ICT-Bèta | Department of Science |  Utrecht University |
>  
>