In order to boot Clarabyte, SecureBoot features have to be disabled within the BIOS and USB boot must be enabled. The HP Elitepad's allows you to access the Pre-Boot Menu by pressing the Volume Down button while powering on the machine. From here however the two models approach BIOS access very differently.
The HP Elitepad 1000 G2 allows access to the BIOS by selecting the option using the touchscreen or by pressing F10 on a connected keyboard.
From there, the BIOS is similar to many HP systems. Go to Boot Options, enable USB boot and scroll to the bottom to disable Secure Boot. You must then return to the main menu to Save Changes.
On reboot the tablet may prompt you that a change was made to the BIOS settings and that you will have to enter the on-screen PIN to continue.
The HP Elitetab 900 G1 however does not allow access to the BIOS settings through the Pre-Boot Menu. In fact, the settings are only configurable through a Windows program to edit the BIOS chip values. We have also confirmed with HP Support, the BIOS is set to only boot devices that at FAT32 formatted with a valid Windows 8 image, and this is not configurable. Unfortunately this restriction prevents Clarabyte from booting.
If you must still erase an HP Elitetab 900 G1 there is an included Secure Erase command in the Pre-Boot Menu. This will send an ATA Secure Erase command to the drive. Of course there will be no reporting available, so the process will have to be documented manually.
If there is no Secure Erase option in your Pre-Boot Menu, this is likely because the BIOS was locked previously or the BIOS is not up to date. Use the HP Recovery option (F11) to completely reinstall Windows, and download the HP Software and Drivers to manage the BIOS settings and update to the latest version. Once they are installed the BIOS settings can be set by opening the Control Panel. On reboot, the Secure Erase option should be visible in the Pre-Boot Menu.