Looking for some clarification about windows XP SIDs.

I'm currently adding a Windows domain to my existing network and use ZEN imaging to image PC's. Sysprep was not used in the past to generate these images so I was expecting the SIDs on all the PC's to be the same. After looking at the SID using ziswin I have found they are different.

Does the zfdagent regenerate the SID on XP workstations after imaging?

Thank you.