I came across this on Boing Boing where it was linked from another blog. It's pretty right on.
1. Word processors never display a cursor.
2. You never have to use the space-bar when typing long sentences.
3. Movie characters never make typing mistakes.
4. All monitors display inch-high letters.
5. High-tech computers, such as those used by NASA, the CIA or some such governmental institution, will have easy to understand graphical interfaces.
6. Those that don’t have graphical interfaces will have incredibly powerful text-based command shells that can correctly understand and execute commands typed in plain English.
7. Note: Command line interfaces will give you access to any information you want by simply typing, “ACCESS THE SECRET FILES” on any near-by keyboard.
8. You can also infect a computer with a destructive virus by simply typing “UPLOAD VIRUS”. (See “Fortress”.)
9. All computers are connected. You can access the information on the villain’s desktop computer even if it’s turned off.
10. Powerful computers beep whenever you press a key or the screen changes. Some computers also slow down the output on the screen so that it doesn’t go faster than you can read. (Really advanced computers will also emulate the sound of a dot-matrix printer.)
11. All computer panels operate on thousands of volts and have explosive devices underneath their surface. Malfunctions are indicated by a bright flash of light, a puff of smoke, a shower of sparks and an explosion that causes you to jump backwards.
12. People typing on a computer can safely turn it off without saving the data.
13. A hacker is always able to break into the most sensitive computer in the world by guessing the secret password in two tries.
14. You may bypass “PERMISSION DENIED” message by using the “OVERRIDE” function. (See “Demolition Man”.)
15. Computers only take 2 seconds to boot up instead of the average minutes for desktop PCs and 30 minutes or more for larger systems that can run 24 hours, 365 days a year without a reset.
16. Complex calculations and loading of huge amounts of data will be accomplished in under three seconds. Movie modems usually appear to transmit data at the speed of two gigabytes per second.
17. When the power plant/missile site/main computer overheats, all control panels will explode shortly before the entire building will.
18. If you display a file on the screen and someone deletes the file, it also disappears from the screen (See “Clear and Present Danger”).
19. If a disk contains encrypted files, you are automatically asked for a password when you insert it.
20. Computers can interface with any other computer regardless of the manufacturer or galaxy where it originated. (See “Independence Day”.)
21. Computer disks will work on any computer has a floppy drive and all software is usable on any platforms.
22. The more high-tech the equipment, the more buttons it will have (See “Aliens”.)
23. Note: You must be highly trained to operate high-tech computers because the buttons have no labels except for the “SELF-DESTRUCT” button.
24. Most computers, no matter how small, have reality-defying three-dimensional active animation, photo-realistic graphics capabilities.
25. Laptops always have amazing real-time video phone capabilities and performance similar to a CRAY Supercomputer.
26. Whenever a character looks at a monitor, the image is so bright that it projects itself onto their face. (See “Alien” or “2001″)
27. Searches on the internet will always return what you are looking for no matter how vague your keywords are. (See “Mission Impossible”, Tom Cruise searches with keywords like “file” and “computer” and 3 results are returned.)