You should perform an software using AltBoot procedure with FORCED_UPGRADE and DISABLE_DATA_BACKUP options if you want to erase all the previous customer settings.
Unfortunately you cannot. And for the future, save a clone with the machine setting every time you change something, so you can reinstall the clone with the latest settings.
I have a very old 5765 which has served us well over all these years. However, Xerox needed to replace the motherboard and we lost all our settings. Needless to say, the motherboard was used (no new parts for these old machines). When I tried to read in my old email addresses from the *.csv file, I received an error message regarding the LDAP settings. We did not have the machine set up for LDAP, but apparently the prior owner of the motherboard did. So, I cannot read in my email addresses.
How do I get rid of the prior owner's settings? I know how to pull in the email addresses from the *.csv file, I've done it many times over the years.