The IBM 600 can have three types of passwords:
- Power On Password
- Supervisor Password
- Hard Disk Password
This looks like a hard disk password issue.
The
Thinkpad 600X Hardware Maintenance Manual states:
Note: The supervisor password and hard disk password cannot be replaced if they are forgotten. If the customer forgets the supervisor password, the system board must be replaced. If the customer forgets the hard disk password, the hard disk drive must be replaced.
For more information, check the
IBM 600 Technical Reference.
I would return that used hard drive which you bought and complain to the seller for providing you with a password-locked hard drive.