Inside the Dell Utility Partition

An Exploration by Dan Goodell
Introduction Partition Parameters Sealed State Unsealed State Recreating Customizing
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.
Warning: If your computer is equipped with a Dell PC-Restore partition, that feature expects to return the computer to a sealed state following a restore of the operating system. To avoid overwriting your custom config.sys and autoexec.bat files, you should edit the PC-Restore partition's autoexec.bat file so it skips that step.

Breaking Into the Utility Partition

To add additional files, you need access to the partition. First, use ptedit (don't forget to load a mouse driver) to change the partition-type to 06, and make it the active partition so it will be accessible as C:. You can't boot directly to C: yet because you have to first break the automatic delldiag-and-reboot cycle, so reboot from a DOS floppy or some other DOS boot disk, such as a CD or flash drive. Now C: should be your visible Utility partition. Rename c:\autoexec.bat to autoexec.old to prevent it from automatically running. With autoexec.bat out of the way, you can now reboot directly to the Utility partition and have access to its files, without it automatically rebooting on you.

Add files and test everything. As long as the partition is active, the computer will boot the utility partition instead of the Windows partition, so take advantage of that by rebooting and testing how the partition works.

After adding files and making sure the partition operates like you want, use ptedit again to change the partition-type and active partition back to the way they were. Now you can run your own utilities from Dell's Utility partition.

I leave it to the reader to know enough DOS to customize the partition to your own liking. I'm not here to provide DOS support, but will offer a few ideas.

The first customization I recommend is upgrading the DOS version to MS-DOS 7.1, the version in Windows 98. This enables access to other FAT32 partitions from the Utility partition, not just FAT16 partitions. This is done by booting from a Win98 boot floppy and using the command "sys c:". Also change any associated DOS files (himem.sys, emm386.exe, etc.) to the Win98 versions.

Another partition layout that might be useful would be to include a FAT32 partition at the end of the disk or on a second disk, which can then be used as a storage location for backup images of the main Windows partition created with non-Windows partition-imaging utilities.

I use a DOS menu similar to that shown at left. This particular menu utilizes the DOS ansi.sys driver (loaded via config.sys) to manipulate screen colors, and DOS's to wait for a keypress to act on. Type "choice /?" for help with the choice command (well, a little help, anyway). Ansi.sys recognizes special "escape sequences" embedded in the menu batch file to specify screen characteristics like text and background color.

Note I haven't dumped the original Dell Diagnostics utility -- it's included on the custom menu. Returning from DellDiag returns to the menu instead of automatically rebooting.

If it's of any help, I've made available some of the DOS files I use. Download (1.9 MB). Extract custom.exe from the zipfile, place it in the root directory of your Utility partition, and run it from the DOS command line to extract the directories and files. If you'd rather see what's in it first, place it in a temporary directory and run it to extract the directories and files into the temporary directory, then move them to the root directory.
(Note to reader: Why is custom.exe a self-extracting archive file? Because it's the easiest way to recreate the directory structure along with the extracted files. So, why re-zip custom.exe into Because nearly everyone can download zipfiles, but some people may have trouble directly downloading an executable file like custom.exe due to security settings on their Internet connection.)
Feel free to customize the menu to your own liking and add your own utilities.


Unfortunately, customizing the Dell Utility partition is less useful on recent Dell models. As of sometime around late-2007 or early-2008, Dell began including a "Pre-boot System Assessment" (PSA) feature in the bios. PSA runs a whole series of diagnostics tests, and can typically take 10 or 15 minutes to finish.

When you press F12 at boot time and select "Diagnostics" from the one-time boot menu, the bios launches PSA before turning to the hard disk and finally booting the Utility partition. PSA is built into the bios, and I am not aware of a way around this.

While you can still customize the partition, it's just not practical to use if you have to wait 10 or 15 minutes before getting to your custom menu! While I still customize these partitions on my own systems, I've gone back to configuring it as a standard multiboot system using a third-party boot manager instead of using the F12 bios boot menu and the DE type code.

author: Dan Goodell