What exactly does sysprep do and when should it be used? I deploy many VMs and VDIs by cloning other VMs or deploying from templates. I am working on updating the base images and have done all other changes needing to be done. Now that I'm ready to start deploying from them I'm wondering if it's advisable to sysprep and if I need to do it on each deployment or only once on the base image? I've had some people tell me that sysprep should not be run on virtual machines.

I'm using vSphere Client version 5 and am mainly dealing with Windows 7 and Windows Server 2008 R2.

Here's one more question. If sysprep only needs to be done on the base image how come everyone's up in arms that there's a [limited number of times sysprep can be done on a copy of Windows 7](https://www.google.com/search?q=number%20times%20windows%207%20sysprep&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a)?

Aside from the SID what does sysprep change?