Microsoft Word for Windows introduced the Tip of the Day feature, which presents a helpful tip every time you start a tip-enabled application such as Win95, Office 95, and NT 4.0. You can add your own set of tips. This is a workstation option, not a useful server hack. The list of tips are stored as a set of values under:

Hive: HKEY_LOCAL_MACHINE
Key: Software\Microsoft\Windows\CurrentVersion\Explorer\Tips
Name: 0
Type: REG_SZ
Value: your-tip-0
Name: 1
Type: REG_SZ
Value: your-tip-1
You can replace any of the existing tips included with NT by changing that tip's value. Alternatively you can replace all of them by removing all the values under Tips and replacing them with your own. There is a pair of REG_BINARY values which control whether and which tips come next. These values are stored in HKEY_CURRENT_USER, so they can be different for every user.

Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Explorer\Tips
Name: Show
Type: REG_BINARY
Value: 00000000 disables the tip
Value: 01000000 enables the tip

The Next subkey controls order of display.
Hive: HKEY_CURRENT_USER
Key: Software\Microsoft\Windows\CurrentVersion\Explorer\Tips
Name: Next
Type: REG_BINARY
Value: 00000000 displays tip 0
Value: 01000000 displays tip 1
Value: ... displays tip ...
Value: 0c000000 displays tip 12

NT will automatically increment and update this value as each tip is displayed.