Some recent downloads from Microsoft

Windows Desktop Search 3.0
The search engine in WDS 3.0 is a Microsoft Windows service that is also used by programs such as Microsoft Office Outlook 2007 and Microsoft Office OneNote 2007. You can use this search engine to index a program's content and to obtain instant results when you search in a particular program. WDS 3.0 supports the following operating systems:
– 32-bit versions of Microsoft Windows XP with Service Pack 2 (SP2)
– All x64-based versions of Windows XP
– Microsoft Windows Server 2003 with Service Pack 1 (SP1)
– All x64-based versions of Windows Server 2003

You cannot install WDS 3.0 on a computer that is running Windows Vista. WDS functionality is already built into Windows Vista. WDS 3.0 provides fast indexing, improved performance, and improved file type support. The WDS 3.0 installation process automatically upgrades WDS 2.5 and later versions of WDS. If you have an earlier version than WDS 2.5 installed, use the Add or Remove Programs tool to remove the earlier version before you install WDS 3.0.

One of the features in Windows Vista that I most enjoy is the search. Now, Windows XP users can get this search capability as well. Go get it - it rocks!

Microsoft Application Verifier 3.3
Application Verifier is a runtime verification tool for unmanaged code that assists in quickly finding subtle programming errors that can be extremely difficult to identify with normal application testing.

Application Verifier is designed specifically to detect and help debug memory corruptions and critical security vulnerabilities. It makes it easier to create reliable applications by monitoring an application's interaction with the Windows operating system, profiling its use of objects, the registry, the file system, and Win32 APIs (including heaps, handles, locks, and more). It also includes checks to predict how well the application will perform under Least-privileged User Account operation, compatibility tests to be used in logoing, and print tests to verify your usage of the print subsystem.

Running Application Verifier is easy; simply turn on the tool then run your project and go through your normal testing scenarios with a debugger attached. When your tests are completed, view the Application Verifier logs for any errors that may have been detected.

Also check out Using Application Verifer Within Your Software Development Lifecycle

Microsoft Standard User Analyzer
The Standard User Analyzer helps developers and IT professionals diagnose issues that would prevent a program from running properly without administrator privileges. On Windows Vista, even administrators run most programs with standard user privileges by default, so it is important to ensure that your application does not have administrator access as a dependency.
Using the Standard User Analyzer to test your application can identify the following administrator dependencies and return the results in a graphical interface:
• File access
• Registry access
• INI files
• Token issues
• Security privileges
• Name space issues
• Other issues
This tool also complements the Application Compatibility Toolkit (ACT) 5.0. ACT 5.0 will include a User Account Control agent that you can deploy to user desktops to identify applications that require administer privileges. The Standard User Analyzer is designed to be run on the developer or tester’s workstation to test and troubleshoot a specific application. Issues identified with the Standard User Analyzer can also be entered into you ACT 5.0 database so you can track the application compatibility across your environment.

Do you write Windows desktop applications?  This is a must-have for your toolbox, particularly looking forward to UAC in Windows Vista (which is a GoodThing).