Inside the Dell Utility Partition
An Exploration by Dan Goodell
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.
The key combination to do this varies from one machine to the next.
On this test Dimension 4600, pressing F12 during POST
(Power-On System Test) when the computer is turned on will bring up a bios
boot menu, from which the user can select to boot the Utility Partition.
When selected, the bios routine scans the partition table for a partition of type DEh.
If found, it boots that partition, disregarding which partition is marked active in
the partition table.
If no DEh is found, it bails without displaying any error message and proceeds to boot
the active partition instead.
When the Utility partition is booted from the bios boot menu, it's interesting to note
that nothing actually changes in the partition table. The Utility partition is still DEh
and the Windows partition is still marked active.
The bios actually copies the disk partition table into ram and then uses
it like the real partition table. The partition-type is changed from DEh to 06h and the
partition is marked active -- all in the ram copy. Then the bios transfers control to the
active partition in the ram copy.
I have experimentally determined that the bios menu does not require the Utility
partition to be the first partition on the disk, nor does it have to be the first
partition listed in the partition table.
(Note to reader: In case the reader doesn't know this, these are two different things
-- the order the partitions are listed
in the partition table does not necessarily have to correspond with the order of
the physical partitions on the disk.)
However, in order for the Dell bios to be able to boot it, the Utility partition does
have to be within the first 8GB of the disk.
Having been replaced by seal.exe when the system was unsealed, the new
automatically launches delldiag.exe, the Dell Diagnostic utility program.
When delldiag.exe exits, dellboot.exe is automatically executed and reboots the computer.
Although the Utility partition does not need to be the first partition for it to
function, there are practical reasons for keeping it in the first position.
If the computer is equipped with a Dell PC-Restore
partition, that feature requires the Utility partition to be first -- not for the
Utility partition to function, but for the PC-Restore
partition to function correctly.
(Note to self: I haven't determined if the same restriction is imposed by seal.exe.)
Also, version upgrades to the Dell Diagnostics utility are sometimes available
for some models. These upgrades may be supplied in a variety of formats, with
one format (since perhaps 2007?) being a 32-bit executable that updates the Utility
partition from Windows. A user has reported that these Windows versions seem to
require that the Utility partition be first or the update will not proceed.