If you buy a Windows 8-powered HP consumer PC, or from any other PC vendor, you'll get no help from them if you decide you'd rather have Windows 7. And Linux? Forget about it!
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.
Read more at source:
Windows 8 is a one way street for consumer PC users | ZDNet
HP clarifies Windows 8 consumer PC downgrade and warranties