Error Message:

A hard disk can contain four primary partitions, one of which can be an extended partition that can contain an unlimited number of logical drives. Setup has determined that a new primary partition cannot be added on the hard disk you selected because it already contains four partitions. You can do one of the following: Select another disk or an existing partition where you will install Windows 2000. Remove an existing primary partition and create a new partition from the free space. (All data will be lost on any existing partition that you remove.) To return to Setup, press ESC.

Explanation:

The hard disk you selected already has the four primary partitions, and another one cannot be added.

User Action:

Select another disk or an existing partition where you will install Windows 2000 or remove an existing primary partition and create a new partition.