Want to install lenny on older Powerbook G4 mac

[Mark Hoff <mark_hoff@mac.com>]

I am trying to install Debian Linux version 5 (lenny) on an old G4 Powerbook
   (Titanium, 1GB memory, 667Mhz cpu, Machine model version 2.1)
   that is running Mac OS X 10.2.

Some of my constraints:
1) It is not possible at this time to upgrade to a more recent version of OS X.
2) I do not have a wired internet connection from this Mac.
3) The only WIFI access is to a WPA connection (no control over the router either).

More Background:
a) The mac software works just fine (just no internet access due to above).
b) I do have internet access to the wireless router from two other machines:
   - Windows Vista notebook PC (but no Administrator access on this computer)
   - Windows 7 notebook PC (full access to this computer)

What I have tried so far:
1) Downloaded Net Boot CD iso image (from debian.org) and burned a CD with it.
     The install went just fine, until it found several deb files that were 'corrupt'.
     So I downloaded fresh copies of them off the debian web site.
     I just don't know how to integrate them into the install process.

2) Downloaded the first CD iso image from
   [ http://cdimage.debian.org/debian-cd/5.0.1/powerpc/iso-cd/ ].
     Then I burned this CD using the same computer and software as above
     (IsoBuster on a Windows XP machine that has no internet access).
    That CD would not boot on my Powerbook - it has a 'read error' when trying to load the kernel.

I also have an available USB keychain drive (4Gbyes).

What can I do to get Linux installed on my Powerbook?

Thanks,
Mark