For many years, PCs have been running on something called BIOS. Essentially, this was the chip in your computer that allowed your keyboard, mouse, monitor and other components to work when turning on. However, there is something similar and newer that does the same job called UEFI(Unified Extensible Firmware Interface). It will allow your computer to boot up faster amongst other things.
Of course, Windows 8 will be taking advantage of UEFI, meaning you could have a Windows 8 PC with a decent boot time. However, there is a sting in the tale. When windows 8 is released, manufacturers will be putting Windows 8 on the PCs that they sell. However, the PCs must have UEFI, which also has a secure boot feature(which must be enabled). If the manufacturers follow this rule, then they can put a sticker on their PCs saying that their PC was designed for Windows 8. Essentially, this means that you cannot install Linux on a Windows 8 PC.
With that being said, you can install VIrtualBox(or VMWare Player) on Windows 8. From there, you can create a virtual PC and install Unbuntu Linux on it. For more information on virtualisation, click here . I know that Microsoft wants to make an effort to secure their operating system, but they have to consider people who want to run Linux alongside Windows.