Computer Cool Tricks

If by trick you mean something cool/weird to show your friends:

1. You cannot name a folder "con".
2. You can name a folder " " by typing in the name as Alt+255 (numeric keypad usage must) and not by pressing space key.

If you seek general tips:

1. Adding "Shift" to any keyboard shortcut generally reverses the effect. e.g. Space can be used to scroll down a webpage. Shift+Space scrolls up.
2. Most system problems can be rectified with a system restart!

If by trick you mean a keyboard shortcut, following are pretty useful:

1. WinKey + E: Open computer.
2. WinKey + L: Lock computer.
3. WinKey + X: Mobility Center (Vista onwards, afaik)
4. WinKey + An arrow key: Tile current window in direction of arrow (7 onwards, afaik)