Quite simply, all you need to do to make a Zipit Z2 new again is to remove a few configuration files. You can do this using either my IZ2S, or even the vanilla Z2 Shell.
Boot up with your shell, and then do a "cd /mnt/ffs" and an "ls" to list the files there. You will see something like this ...
-rwxr-xr-x 1 root root 657 Dec 16 01:58 411.xml
-rwxr-xr-x 1 root root 112342 Dec 16 01:58 NeonGlow.jpg
-rwxr-xr-x 1 root root 1519952 Dec 16 01:58 Resources.arl
-rwxr-xr-x 1 root root 3578680 Dec 16 01:58 Zipit2
-rwxr-xr-x 1 root root 1921 Dec 16 01:58 properties.txt
-rwxr-xr-x 1 root root 4644 Dec 16 01:58 serversettings.xml
-rwxr-xr-x 1 root root 4644 Dec 16 01:58 serverstationz.xml
-rwxr-xr-x 1 root root 510 Dec 16 01:58 start.sh
drwxr-xr-x 2 root root 4096 Dec 16 01:58 wpa_supplicant
Only a few of these files are really required, and the rest are files that get downloaded from Zipit Wireless when your Z2 connects up to their servers through the wireless network.
You can safely remove these files:
NeonGlow.jpg - This is my chosen background wallpaper. Whatever you picked will have a .jpg extension. You can delete any .jpg file here.
properties.txt - This file contains your device ID (serial number), your username, and some other important settings. Deleting this file removes your Zipit Wireless account association.
serversettings.xml - This file contains a record of your messaging limit(s), your chosen wallpaper, and some radio station data.
serverstationz.xml - This file seems to contain the same data as "serversettings.xml". Both files can be deleted and would be recreated when you connect with your Zipit Wireless account.
DO NOT REMOVE (or alter) THESE FILES!
Resources.arl - This is some sort of archive which likely contains data for your theme. Although it's compressed, and I don't know how. Leave it alone.
Zipit2 - This is the core application for the Z2. Do not alter this file, or your Z2 will no longer be any fun.
start.sh - This short and simple script is what allows for you to run a shell, as it looks for an OS on your SD card at boot time. It also runs the Zipit2 application. Leave this alone!
wpa_supplicant - This directory contains an executable of the same name. This is what connects the Z2 to your wireless network. Leave this alone too!
Just to recap ...
If you want to make your Zipit "new again", you should delete your settings files so that your /mnt/ffs directory looks something like this ...
-rwxr-xr-x 1 root root 1519952 Jan 1 1970 Resources.arl
-rwxr-xr-x 1 root root 3578680 Jan 1 1970 Zipit2
-rwxr-xr-x 1 root root 510 Sep 17 2007 start.sh
drwxrwxr-x 2 root root 0 Sep 17 2007 wpa_supplicant
The next time you boot your Z2 (without the SD card inserted) you will get the "first time wizard". By the way, in case you forgot - one of your options in this wizard is to enter the credentials for your existing account.