Etch back to Sarge

[bigoperm <bigoperm@yahoo.com>]

I need to downgrade from Etch back to Sarge. The only resource I have is the original Sarge install CD. How can I use this CD to reinstall Sarge (over Etch) without using any data?

My intuition tells me all I need to do is skip the partition phase of the install, and things should be okay; however to do so requires that a root filesystem must be mounted. Is there a boot option I can pass to the installer to tell it to mount my already existing system? Thanks in advance.