[MovedGoalPosts]

Under normal circumstances each PC needs it's own Operating System. If it's a case that you need a PC to remotely boot up, if it's been shut down (maybe you are using internet connection sharing for example and hte sharing computer gets turned off by the user), some modern PCs have functionality in the network card to enable a remote LAN wake up call. Never tried it, but it'll need settings on both the BIOS and the network card, with a sufficiently modern PC that in fact the LAN card always stays with some power even if the PC appears off.

In some office environments you can get a "thin client" type setup whereby the PC relies on a networked OS. Might be possible with some versions of Linux, but not under windows afaik.