Free Environment Assessment Toolkit
For my desktop deployment projects i recommend to use the Microsoft Assessment and Planning toolkit that will find computers on a network and perform a detailed inventory of the computers using Windows Management Instrumentation (WMI), the Remote Registry Service, or the Simple Network Management Protocol (SNMP).
The data and analysis provided by this toolkit can will help the planning process for several solutions including migrating to Windows Vista, Microsoft Office 2007, Windows Server 2008, Microsoft Application Virtualization 4.5, Microsoft SQL Server 2008, Microsoft Online Services, Forefront and Network Access Protection, Windows Server 2008 Hyper-V, and Virtual Server 2005 R2. Assessments for Windows Server 2008 and Windows Vista also include device driver availability and recommendations for hardware upgrades that may be required.