Read only file FSTAB after error config???

[Soweb_Ahfei]

Dear Sir,   We have installed the Freebsd4.32 in our server.But we can not reboot the system after we made an error configuration  in the file FSTAB.Now,we can not delete or rename the error file Fstab and the system shown the file is read only.   We would not re-install the system since there are some available data.Please give us an instruction how to revise it.   Thanks.   Best regards.   We do need your kindly help!! Ahfei  Ho