• The version of the client that last worked on the packet.
• The operating system that the client that last worked on the packet ran under.
• The processor family that that OS ran on.
• Partially completed packets also contain the core number that last worked on the packet.
• The distributed.net id (email address) of the client that last worked on the packet.
  Note: If you change the email address in the client, only those packets that have yet to be processed/completed will be effected. Previously completed work will retain the old address.

When a partially completed packet is loaded by the client, and the client version or OS or processor family or core-number do not match those of the client that previously worked on it, the packet is treated as if no previous work had been done at all (all work is reset).