two computers one monitor

How to use two computers on one monitor?
I I want to build up a new system just for doing one task alone and it makes no sense I buy another monitor when I already have one.
I want to know how do I use one monitor but have totall controll of two computers?
I mainly want to use the other PC to convert DVD to mp4′s.
I do not want to use a KVM switch.
I want to network both computers.
can anyone please help me.
Buy a KVM solution (Keyboard, Mouse Video switch)
Most PC shops sell them
Usually a hotkey set on the keyboard switched the user from 1pc to other, also use 1 keyboard and mouse, not 2
Micosoft System Center 2010
Last month, Microsoft released the first two products in the System Center 2010 wave: the management suite System Center Essentials 2010, and the backup-and-recovery-focused Data Protection Manager 2010. I’ve been evaluating these products in late prerelease form, and I’ll share my impressions and what I’ve discovered here.