Hi Lee
I think it depends on the number the company is in the company list. If they are company 1 then its relatively straight forward.
- mark the unwanted companies as deleted in admin mode
- export import
- delete the unwanted companies from the register
Unfortunately, if they are not company 1 then you I think you have to build a new hdb and import the company backup into it. You lose your attachment links unfortunately. Can be solved with hal i believe.