You could probably do it over LAN somehow, supposing that the BIOS would allow that. (Most BIOSes have some sort of network boot support)
If it's a really old PC, it might not work. (Read on anyway)
However, you might need a couple other things:
1. Either a boot ROM chip that plugs directly into your NIC card, or a network boot floppy. The floppy is probably the more viable option because you'd need to have a way to program an EPROM yourself (let alone obtain a suitable chip).
I'm not 100% certain, but some computer BIOSes may contain a network bootloader built in, making the need for a floppy or NIC boot ROM nonexistant.
2. A BOOTP server running on your network. This supplies the data that the system downloads to boot from the network.
Any networked system should be able to do it, it's a combination of a DHCP and a TFTP server.
3. Connect the Wake On Lan cable from your NIC card to your mobo, if you want to be able to boot up the machine from somewhere else on the network. It's a 3 pin cable.
As for the OS used, you could probably get linux on it. Once it was installed this would let you use the machine (as you would have ssh to it and thus could control it from another machine).
If your PC is from 2001 or later, it should support the PXE standard to boot machines from the network.
I don't know a lot about booting machines this way. However, do read these pages:
http://www.linuxfocus.org/English/Septembe...article63.shtmlhttp://www.kegel.com/linux/pxe.htmlThese have some pointers on booting a linux installer from the network.