Installation doesn't recognise my extended partition

[David Jarvie <lists@astrojar.org.uk>]

I am trying to install Debian (version 3.0) for the first time. I already have 
another Linux system installed on logical partitions within an extended 
partition (on an Athlon system), and have created a new logical partition to 
install Debian into. But when I run the installation CD, it sees but fails to 
recognise the extended partition, and therefore doesn't see the logical 
partitions within it. The reason is, I think, that the extended partition has 
a partition type of 0x0f rather than 0x05 which appears to be the standard 
code for an extended partition. (The partitions were created by System 
Commander.)

How can I make the installation program see my logical partitions? Can I patch 
and rebuild a program in the installation CD, and recreate the CD? Or 
alternatively, how could I change the partition type code from 0x0f to 0x05 
without losing any of the data on the partitions?

--
David Jarvie.