Traditionally an ATA disk password will not enable encryption for data at rest on the disk. BIOS factory reset will not reset what is known as the ATA User password. The ATA Master and User passwords are stored on the disk drive's physical firmware.
The drive can be unlocked using a (factory-installed) Master password (which generally only becomes relevant when the User password is set) or using the User password.
For some fun background reading on the the use of ATA passwords and disk drives refer to the T13 Working Group ATA Command Set (search the PDF for
There are several tools and techniques available to obtain the Master password depending on drive type.
I have not had to workaround a Seagate drive, but the general order involves feeding a manufacturer specific script (available on forums) to a tool like MHDD or Victoria to dump data located in the drive's firmware which contains the Master or User password, parse and translate (with your brain) the output with a hex editor to yield the Master or User password, and then use MHDD or Victoria to unlock the drive with the password.
There are many posts on hddguru forums outlining the process for various manufacturers and drives.