How does a client know about "Custom Data"

I would like to understand how the "Custom Data" in the inventory is setup on the client.

Here is what I see

Client is having problems, so we Reinstall the landesk Client.
This does not fix the users problem, so I run the Landesk Client uninstaller.
Reboot and reinstall the landesk client.

Now the client is working but is not reporting back "Custom Data" in the Inventory.
All other inventory is collected but not "Custom Data"

So how and what is updated on the client to know what "Custome Data" to send?
Is it a reg key or file? And If a client will not report back "Custome Data" what can you try on the client?