I've been looking at making a Info Report for a client that shows the Age of the system (when it came online if at all possible), if it is still checking in, the amount of RAM it currently uses and last user login, OS and System Serial Number. The closest I have come to it has been setting up 2 different tables, one has computer name, last user logged on and transitions time and the other has computer name, serial number and OS. If at all possible it would be nice to set this up as 1 table, if not 2 would work I just can't seem to find a way to show when the computer was first put online.
The VSA records the first checkin date/time (first time the *agent* checked in, not the overall age of the machine). The true machine age - that's tricky - pretty much no weay to know this with any certainty.
Look in report parts - agent - agent configuration - "First Checkin" field, if you want to build something around the first checkin time.
We use something like the solution here presented at community.kaseya.com/.../86951.aspx to populate a custom field with the OS installation date so that we can later report on it.
As Craig points out this is not always accurate (e.g. VMs cloned from a template will show the templates OS installation date) but it's better than nothing.