Standard inventory on managed computers collects more than 100 predefined data classes. Inv_SW_Patch_Windows belongs to Hardware group of data classes. You may experience a situation when an inventory task has completed successfully but Inv_SW_Patch_Windows is empty.
The following message can be seen in Altiris logs
The inventory for [SW Patch Windows] is an empty string, will create an empty NSI.
The following query is used to populate the data class
select HotFixID,InstalledOn,InstalledBy,Description,ServicePackInEffect,FixComments from Win32_quickFixEngineering.
The query has a predefined 2- minute timeout. The data class is populated with empty data if it takes more than 2 minutes to complete the query.