If you want to wipe out and create a new MOSS Farm here are the steps
+ Run the Configuration Wizard and, on the second page, select Disconnect from this server farm and click Yes on the warning dialog. This will delete the IIS web site and the application pool.
+ Then, run the uninstall from the Control Panel's Features and Programs application and click Yes on the warning dialog. This will take a reboot.
+ Then, if you really want to get rid of it all, go to the database server and delete the Config and Admin Content databases
Alternatively you can also disconnect the central admin from the 12 hive using cmd line if nothing works:
psconfig -cmd adminvs -unprovision
psconfig -cmd configdb -disconnect