Error while restoring backup in NF 2.01B

I have got error while restoring backup. At first it showed after all data were copied, at the end of key optimisation, and error was: (Translation to english): “Database has corrupted area.This error can arise if database has been changed by another programm or device’s driver isn’t working properly. … {Then there is explanation of how this could be treated, including database check}”. Then a new database was created and there was another try to restore the backup. At the end of data copy process showed another error (Translation to english): “Backup has been corrupted (wrong checksumm)” Database is about 8GB and has about several M G/L and Item ledger entries. Database check showed nothing except some missing table relations, but they were missed a long time ago when there were no problems with restore… What should be done? In which direction should I think now?