Please check the following Microsoft Knowledge Base article:
http://support.microsoft.com/kb/260233/
SYMPTOMS
Windows 2000 does not support ATA-100 (Mode 5) for IDE hard disks. All ATA-100 IDE hard disks that are used with Windows 2000 default to ATA-66 (Mode 4).
RESOLUTION
A supported fix that corrects this problem is now available from Microsoft, but it has not been fully regression tested and should be applied only to computers that are experiencing this specific problem. If you are not severely affected by this specific problem, Microsoft recommends that you wait for the next Windows 2000 service pack that contains this fix.
To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. ...