I have a old Windows PC named pc1 which is joined to domain1 currently. However. today I tried to join the same domain with a new different computer with same OS version, MAC address and computer name. It prompted up:

The join operation was not successful. This could be because an existing computer account having name "pc1" was previously created... Access Denied

After some research, I found that the AD has the information (SID) of my old computer. May I know if I can replace this "SID" with my new computer in order to make it joins the domain? Or what can I do to make it if I do not have the administrator rights?

Or should I ask: How can the AD recognize my computer if I get a same pc name, MAC address and OS version?

  • 1
    Why does your new pc have the same MAC address? MAC addresses are meant to be unique for each network card and without intentional spoofing they shouldn't be the same. Regardless of all that, OS version and MAC address shouldn't be what's causing the issue here. Have you got admin right's to either PC? You can change the name on either one so there's no more conflict in the names.
    – Gytis
    Aug 20, 2018 at 9:28
  • 1
    May I know if I can replace this "SID" with my new computer in order to make it joins the domain? If you try to alter your station's local SID you will damage your OS. If you try to alter SID of a station object info in AD you may damage the domain partially or whole. DO NOT TRY TO DO IT !!! simply remove old Station object from the domain and create new one.
    – Akina
    Aug 20, 2018 at 9:34
  • @Akina does it means that I can't make it without administrator rights?
    – mannok
    Aug 20, 2018 at 9:39
  • Maybe so, maybe not. I know nothing about your domain.
    – Akina
    Aug 20, 2018 at 9:45

1 Answer 1


The account's SID is not important here – it's just a serial number. Active Directory accounts are based on the computer's name, and each joined computer knows the "password" to its own account. You can't have two accounts with the same username.

(Local machine SIDs are not stored in the domain at all, while domain SIDs are always assigned automatically off a counter, so "this SID already exists" cannot realistically happen.)

It doesn't matter what OS or what MAC address you have – if they're two separate computers to be joined simultaneously, they need different computer names.

On the other hand, if the old computer has been decommissioned, ask the AD domain administrator to "reset" the computer account (or delete it entirely, whatever their practice is). If reset it will have a blank password and allow a new join.

Alternatively, if you can, unjoin the old computer first.

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