Consider the following scenario:
In this scenario, Asset Intelligence does not collect the SMS_InstalledSoftwareMS reporting class on the client that is running the Windows 2000 operation system.
If this sounds like an issue you're running into then we have a hotfix that should resolve it. See the following Knowledge Base article for all the details:
KB980488 - Asset Intelligence does not collect the "SMS_InstalledSoftwareMS" reporting class on an SCCM 2007 client in a Windows 2000 operation system
J.C. Hornbeck | System Center Knowledge Engineer