List of Bug Codes (Knowledge Base article for STOP error messages)
Error Codes - Part 1
Error Codes - Part 2
RAS Event ID (Error Code) Information

Compatibility Databases

Find a Logo'd Product combines both the Software and Hardware searches into a much nicer interface than the previous databases.

Resources

Microsoft Online Support Area (from which you can query the Knowledge Base)
How to Search Windows NT Articles by KB Subcategories

Files

Internet Resources for Windows NT is a list of third party utilities for NT
Updates to the Resource Kit

For security bulletins listed by product or date

For Windows Scripting Host, documentation, and examples.

For all the necessary updates to NT 4.0 for Y2K compatibility.