LANDesk's inventory holds the software & hardware information only. And we have a tool called "custom data form" which is used to gets some information as an end-user input and adds that information into the inventory.
So there is no simple way to track PC purchase date.
Software inventory : Installed application, OS Name, OS version, Logon user, local users and groups, etc.,
Hardware inventory: Processor, RAM, Hard disk, PC Model, Manufacturer, etc.,
Custom Data Form : Physical location of the machine, Department, Manager, Team, Designation, etc., (Which is not available in the default LANDesk’s inventory)
We are doing something similar. We purchased an add-on from Managed Planet that allows us to add in other data fields. As we receive equipment we use a bar code scanner to enter them in to the database and this also puts in the date received.
For pre-existing systems that we don't know this info we make a best guess based on various other data fields (warranty info, etc). Managed Planet allows us to calculate new fields based on other fields in the database.