My server crashed. most stuff lost.  I recovered the .mdf .ldf files through DaRT. I can not use the files. It advises that the header is corrupt.  Please advise what the best way to resolve this is.

Use your most recent backup taken for the database. File recovery such that you have tried has little chance for success (as you have noteiced) so restoring a SQL Server backup is most often the only solution.

If you cannot attach the files, then I agree to TIBOR, use your most recent backup to restore the Database. If the DB was using a FULL recovery model with frequent T-Log backups, You should be g

Fully agreed with TiborK but I don't think you have backup of database as you have already tried data recovery tool to recover your mdf/ldf files.

SQL database can be repaired by DBCC CHECKDB's repair options but there is risk of data loss.

• Set database in single user mode
• Run DBCC CHECKDB with repair_allow_data_loss
• Set database in multi user mode

Hope this will helpful for you!!