I think aFoP is right in suggesting to set the HDD as primary boot device. You may have removed Windows from the harddrive but in the UEFI firmware settings it may still be configured to boot the Windows OS in UEFI mode that is no more.
If you followed the how-to correctly and installed Ubuntu in UEFI mode on this new machine it usually creates an ubuntu
boot entry and sets it as the primary boot option, but HP UEFI firmwares have sort of "ignored" this in the past (accepting the command and creating the entry but…) after rebooting they still expected to boot Windows.
For UEFI-installations disabling any Fast Boot option¹ in the firmware setting, optionally disabling Secure Boot and installing the bootloader with the --removable
option to boot from the HDD/SSD should give you a booting OS.
For MBR-installations just disabling UEFI and booting from the HDD/SSD should work as aFoP described.
¹ Apparently managing the boot order to have your favorite OS in first position, detecting drives (disabling slow drives like FDDs, ODDs, big HDDs) and operating systems was so hard that this switch had to be invented, which boots nothing else than Windows and saves a few nanoseconds over a properly configured setup that boots Linux.
"signature verification"
" being in place unless you did sophisticated reverse engineering like this guy and actually found a mechanism like that. – LiveWireBT Jan 18 '15 at 10:22SecureBoot
was all about. – Omio Jan 19 '15 at 13:59