Here are several very good mostly freeware utilities for providing useful information about your hardware, OS, and software from DC member Veign's blog.
1. Autoruns: The most comprehensive knowledge of auto-starting locations of any startup monitor, shows you what programs are configured to run during system bootup or login, and shows you the entries in the order Windows processes them. These programs include ones in your startup folder, Run, RunOnce, and other Registry keys.
2. Everest Home: EVEREST Home Edition is a freeware system information, system diagnostics and benchmarking solution for home PC
3. Application Monitor: A very small API monitor that allows the user to monitor the APIs called by the given application.
4. Shell Extensions Manager: The ShellExView utility displays the details of shell extensions installed on your computer, and allows you to easily disable and enable each shell extension.
5. Win Updates List: Displays the list of all Windows updates (Service Packs and Hotfixes) installed on your local computer.
6. Index Dat Spy: Index.dat are files hidden on your computer that contain all of the Web sites that you have ever visited. Every URL, and every Web page is listed there. Not only that but all of the email that has been sent or received through Outlook or Outlook Express is also being logged.
7. Why Reboot: Displays a list of "pending file operations" (rename, delete, etc) that will occur after rebooting your computer.
8. Process Monitor: An advanced monitoring tool for Windows that shows real-time file system, Registry and process/thread activity.
9. Start Up List: A simple tool that lists all and every auto starting program on your system. (from the developers of Hijack This)
10. Ethereal: Ethereal is used by network professionals around the world for troubleshooting, analysis, software and protocol development, and education...