So, in essence, you should complete the following steps in order to install CeBootLin:
1. Download CeBootLin.
2. Unpack the downloaded archive into the PDA root. The CeBootLin.exe must be reachable with the path \CeBootLin\CeBootLin.exe.
3. Place default.txt under the \CeBootLin directory. The default txt might looks like this (if the Andorid is what you are going to load with CeBootLin):
set MTYPE 1454
set KERNEL "\CeBootLin\zImage"
set CMDLINE "root=179:3 mem=62M rootdelay=3 boot_delay=0 init=/init console=tty0 fbcon=rotate:0 androidboot.console=tty0 android.checkjni=1"
set RAMADDR 0xA0200000
4. Place zImage under the directory \CeBootLin\.
5. Modify HKEY_LOCAL_MACHINE\init adding Launch82 ="CeBootLin.exe" and Depend82 = 14 00.
6. Modify HKEY_LOCAL_MACHINE\Loader\SystemPath adding a new directory \CeBootLin\ to the multi-string list.
7. Wait for 5 minutes (WinCE needs time to persist changes to registry).
8. Feel free to reboot your PDA
To test that CeBootLin is able to boot linux at all, run CeBootLin.exe manually.
It looks little bit complicated but later, setup program might be created to ship automatically bootable Andorid on Loox550. But before, Andorid must be polished.
Here is the source code of CeBootLinux. CeBootLinux is licensed with GNU GPL.