If your 7ZXR PCB revision is 1.0 (Southbridge: VIA 686A), ATA 100 transfer rate is only supported at IDE 3 and 4 from Promise controller. The Promise IDE controller has its own BIOS and will show its details later after POST, it won't be shown in the BIOS setting. Please wait and let the computer continue to boot, then you can see the HDD ATA details if your HDDs are connected in IDE 3 and 4.
If your 7ZXR PCB version is 2.1 (Southbridge: VIA 686B), all IDE 1 to 4 channels can support ATA100 devices. You can see the HDD details in POST and in the BIOS setting when HDDs are connected in IDE 1 and 2. Details of HDDS connected to IDE 3 and 4, please see their information under Promise controller bios.