Are u using Active directory? Is that possible some Group policy make this?
Just random guessing, if SAP B1 uses windows registry to hold that value, then group policy will be one to check. If not windows registry, then it might be an xml configuration file, but for unknown reason, even ur local admin can not change it. So you will need to check ownership of that file.
Anyway, this is just some direction you might want to search.
Frank