I am getting an error 603 on database recovery in a SQL 6.0 system.

A. This happens only on SQL 6.0 SP3. There is no fix, but the workaround is :-

1. Stop SQL Server
2. Rename sqlservr.exe in <sql>\binn to sqlservr.sp3
3. Copy the sqlservr.exe from your SQL 6.0 CD into <sql>\binn
4. Re-start SQL Server. It should now recover ok.
5. Stop SQL Server
6. Rename <sql>\binn\sqlservr.exe to sqlservr.org for later use
7. Rename <sql>\binn\sqlservr.sp3 to sqlservr.exe
8. Re-start SQL Server