To install the diag partition you MUST fdisk the partition and remove all previous partitions. I just upgraded the Diagnostics partition and thought that, since the information in the FAQ is a little sparse, I'd let people know how it works. For Windows users, Compaq provides two kinds of diagnostics utilities. One is Compaq Diagnostics for Windows. It can be obtained from the Compaq FTP server as SP2640.
Installation is no problem.
This is what I just upgraded, and in the process, I ran into a problem or two. That's what the following is about. The other is Computer Setup and Diagnostics for Portables, or SP2054, listed under Utilities. The right one is SP2054. Both disks are needed to upgrade the Diagnostics partition.