PC companies call it downgrading, but many users just call it being sensible. You buy a new computer, and instead of using the bleeding edge operating system it came with, you move to an operating system you trust. With ordinary Windows 8 on Hewlett-Packard (HP) consumer PC, or any other vendor's retail PC, though, you're stuck with Windows 8.
HP's Windows 8 FAQ reads, "Downgrading is supported only for HP commercial desktop and notebook products." That is to say systems that come with Windows 8 Pro. In any case, "HP does not recommend downgrading on any HP consumer desktop and notebook products. After October 26, 2012, HP consumer desktop and notebook products will ship only with Windows 8."
Why? Because "Windows 7 will not be supported on these new platforms, and no drivers, apps, or Windows 7 content will be available through HP. If users choose to downgrade their HP consumer desktop or notebook system, HP will continue to support the hardware but if there is an issue where HP diagnostics are required OR it is determined that the loaded software or upgrade operating system is causing the issue, HP may suggest returning the system to the original Windows 8 OS that shipped with the computer."
In short, if you downgrade anyway, HP is saying you'll be your own. Good luck with that.
HP isn't the only company taking this path. Lenovo doesn't spell it out as clearly, but it doesn't require too much close reading to see what you can't downgrade from consumer Windows 8 to Windows 7 on their PCs and laptops either.
Oh, and XP? It's history. Even if you have a business Windows 8 PC with Windows 8 Pro, you can only move to Windows 7 Professional or Windows Vista Business.
None of this will be surprising to Windows professionals. Microsoft spelled this out in their new Windows 8 licensing agreement in August . Small businesses that want new PCs and small office/home office (SOHO) users that are trying to squeeze every dime from their hardware purchases may be caught by surprise though. In fact, I know they are because I'm already hearing from users who ended up with Windows 8 by mistake or mis-adventure, and they're not happy about being "stuck" with it.
Of course, if you move to Linux instead, you really are on your own. Sure, HP supports Linux on its servers, but it's always been of two-minds about Linux on the desktop. True HP supports SUSE Linux Enterprise Desktop (SLED) and Red Hat Enterprise Linux (RHEL) on workstations and it's certified Ubuntu on some HP desktops and laptops, but trying to buy a HP Linux-powered desktop if you're not looking for several hundred desktops at a time isn't easy. Of course, if you install Linux yourself, you'll be doing it without an HP warranty safety net.
That could be a bigger problem that it used to be. All vendors Windows 8 PC now come with Microsoft's UEFI (Unified Extensible Firmware Interface) Secure Boot. This "security" system makes it much harder to boot Linux, or any other operating system for that matter, on a Windows 8 PC.
Thanks to a lot of hard work, it is possible to boot the newest versions of Fedora and Ubuntu on Windows 8 imprisoned systems. Other and older Linux distributions though will be almost impossible to boot or install on Windows 8 systems.
If you want to avoid the Windows 8 trap to move to an older version of Windows, you'll need to buy a more expensive business PC with Windows 8 Pro. Or, you can factory-upgrade many Windows 8 consumer PCs to Windows 8 Pro for an additional $70. If you were to upgrade your PC yourself from Windows 8 to 8 Pro), for less money, I doubt very much that HP would support trying to move from such a configuration to Windows 7..
Windows RT, Windows 8 on ARM processors, can not, of course, use any other operating system. Windows RT UEFI blocks alternatives and there are no other versions of Windows for these devices.
The bottom line is that if you want a Windows 7 PC, or one that you can easily run Linux or another operating system on, you should avoid buying any Windows 8 PC. Fortunately Windows 7 PCs should stay on sale until at least October 2014.