How many monitors can I hook up to my desktop computer?
Answer: For a desktop computer, if you're using a Mac or running Windows 98 or later, you can hook up as many monitors as you have video cards. Basically, you need a separate connection for each monitor. So if you had 3 PCI slots open, you could add three video cards and three monitors, allowing you to have four total screens.
Some video cards have connections for multiple monitors, which would allow you to connect even more displays to your computer. (These cards usually support 2 or 4 monitors apiece.) I've heard of a Mac that ran 14 displays at one time, which is just ridiculous, but nonetheless, cool.