Just curious as to if you replaced the drive with same type such as IDE with IDE or if you upgraded this older system to now take a SATA drive to where you might need a SATA controller driver for Windows 2000 Pro?
If you kept the same IDE drive type, is the jumper installed correctly for MASTER (MA), SLAVE (SL), or CABLE SELECT (CS) ? Look at the old drive and compare jumper location to make sure it matches the new drive.
I am guessing you are able to boot off the Windows 2000 Pro CD and then it comes to a point to where it says hard drive not detected?