WMI "installed" query different from add/remove programs list?

Question

Trying to use WMI to obtain a list of installed programs for Windows XP. Using wmic, I tried:

C:\Documents and Settings\romandas>wmic  
wmic:root\cli>/output:c:\ProgramList.txt product get name,version

and I get a listing of many of the installed programs, but after scrubbing this list against what "Add/Remove Programs" displays, I see many more programs listed in the GUI of Add/Remove Programs than with the WMI query. Is there another WMI query I need to use to get the rest of the programs installed? Or is there some other place I need to look for the rest?

Also, there are two installed programs that are listed in the WMI query that aren't in Add/Remove programs. Any idea why?

Answer 1

All that Add/Remove Programs is really doing is reading this Registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Uninstall

Answer 2

I believe your syntax is using the Win32_Product Class in WMI. One cause is that this class only displays products installed using Windows Installer (See Here). The uninstall registry key is your best bet. Here is some code to monitor the registry key.

UPDATE FOR COMMENTS:

The Uninstall Registry Key is the standard place to list what is installed and what isn't installed. It is the location that the Add/Remove Programs list will use to populate the list of applications. I'm sure that there are applications that don't list themselves in this location. In that case you'd have to resort to another cruder method such as searching the Program Files directory or looking in the Start Menu Programs List. Both of those ways are definitely not ideal.

In my opinion, looking at the registry key is the best method.