Key and SID Issues

I am looking at a mass of workstations which were rolled out by cloning.

Many of them are using the same installation key although they are properly licensed with the (unique) OEM XP Pro stickers on the cases -- it just that the stickers don't match the installation keys.

Some of them have the same SID in addtion to having the same key.

I know how to generate new SIDs. I know how to change the installed keys.

What I am not sure about is the consequences. How is domain membership affected? How are user profiles affected?

Thanks.