Inside the Dell Utility Partition

An Exploration by Dan Goodell
Disclaimer: I am not associated with Dell Computer Corp. in any way, except as an end user. The information presented here does not represent official information from Dell or Dell representatives. This is just some conclusions from my personal exploration of the utility partition on several Dell desktops and laptops. This information is provided as-is, so interested others may look over my shoulder at what I've found with this particular machine. Though it may apply generally to many new Dell computers, the reader should take that into consideration.
Recent Dell computers come with a hidden Dell Utility partition at the front of the disk. By pressing the right keys while the computer is starting up, the bios startup procedure will pause and display a boot menu from which the user can choose to boot this utility partition instead of the normal Windows partition.

The Dell Utility partition exists in one of two states. It's convenient to think of these two states like opening a factory-fresh package in which the package is initially sealed, and then you break the seal and open the package.

A new computer arrives from Dell in the "sealed" state. When the computer is booted from the hard disk for the very first time, the user must acknowledge the Dell End-User License Agreement (EULA), is prompted to record the Dell Service Tag for future reference, and then the computer is allowed to boot into Windows. Once the seal is broken (that is, the computer has booted at least once), this first-time procedure is not repeated. After the computer has booted once in the sealed state, it changes itself to the "unsealed" state. The Dell Utility partition becomes dormant and does not boot again unless the user deliberately launches it from the bios boot menu. Otherwise, the computer boots directly into Windows.


Partition Parameters
The Dell Utility partition is really an ordinary FAT16 partition (type 06h), but the partition descriptor (a 16-byte pointer in the partition table) has been altered to show a partition-type code of DEh instead of 06h (in hexadecimal notation). This section describes in more detail the parameters of this partition.


Sealed State
In its sealed state, the Utility partition is marked as the 'active' partition in the partition table. Thus, the first time the computer boots from the hard disk it will boot the Utility partition, not the Windows partition. This section describes this one-time-only scenario.


Unsealed State
Once the Utility partition has changed into its unsealed state, it is no longer the active partition. The computer will boot directly into Windows unless the user deliberately opts to boot the Utility partition from the bios boot menu. In that event, the Dell Diagnostic program, delldiag.exe, is launched directly from the Utility partition. This section describes this process in more detail.


Appendix: Recreating the Dell Utility Partition
You may wish to recreate the Utility partition if the hard disk is upgraded or replaced. For the record, installing the Dell Diagnostics utility on the hard disk is optional because you can run the same program from the Dell Resource CD (if one came with your computer -- and if you can still find it) or download it separately from the Dell website. Many people are satisfied to just run the diagnostic utility from CD when needed, and don't find it necessary to duplicate it on the hard disk. This section, however, describes how to recreate the Utility partition on the hard disk if you choose to do so.


Appendix: Customizing the Dell Utility Partition
The typical Utility partition, as created by Dell, is about 30-60 MB large and contains about 10 MB of files. This means there is some extra room to add a few customizations of your own. (You can even enlarge the partition if you want to use more room than 60 MB.) The usual case of booting the Utility partition will launch straight into the Dell Diagnostics utility, and then reboots the system when DellDiag is exited. However, the partition can be customized to launch a simple menu instead, from which you can choose your own custom utilities to run, and returning to your menu instead of automatically rebooting. This section explains how to do this.


Appendix: The Dell PC Restore Partition
(Note to reader: this is separate from, and unrelated to the Utility partition.)


author: Dan Goodell
last revised: 02/15/2011