Houw could I run two computers through one monitor? I want to be able to switch back and forth from one computer to the other.
you would need a linskey KVM or similiar if you wanted to switch the keyboard,mouse and sound too but they start at about $170 otherwise cablestogo you can get a cord for two monitors for about $50
Heheh nicely posted. A KVM (keyboard video mouse) is still what you want though. I don't know why cube said sound, because some KVM units don't carry over nothing else but the K/V/M components. And you can get them for way cheaper than cube quoted you, here for example.
If your monitor has analog and DVI inputs, then you can use them both. A while ago I was running one PC to the monitor using DVI, and another PC using analog. And using VNC to control the other PC from one keyboard/mouse.