PXE code always attempts to set DHCP to option 60 if it detects a Microsoft DHCP server installed on the same system as the PXE server. In some scopes this can cause conflicts
PXE code was designed so that it will always attempt to change DHCP server options to set DHCP option 60 to "PXEClient" if it detects a Microsoft DHCP server installed on the same machine as the PXE server.
Users that are using option 60 in some scopes not in use with PXE have problems with this because it causes conflicts.
In 8.0 HF3, the SBS/PXE startup code checks for the registry key
If that key doesn't exist it will be created as a DWORD with a value of 0.
If it does exist, and is set to 0 (the default) it will keep the current functionality of updating DHCP settings. If the key is found, and is a non-zero value (such as 1) it will still check for DHCP servers installed on the same box, but it will not attempt to set DHCP option 60.