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I need to know what the maximum number of accounts allowed on a Windows 7 system is.

A reference to something official would be ideal. (PHB Situation)

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How is this off topic? It has to do with System Administration? –  Präriewolf Sep 28 '11 at 21:19
    
I don't see much off-topicness here either. Maybe just Pawlows conditioned reflex to reading "Windows 7" (i.e. "not a server O/S"). Flagged it for re-opening, let's see if the question is gonna make it. –  syneticon-dj Sep 28 '11 at 21:29
    
Possibly not off topic, although it sure looks like an end user question, but should have been closed as a dupe of serverfault.com/questions/215405/… –  John Gardeniers Sep 28 '11 at 21:37
    
@JohnGardeniers, I don't think it is a licensing question, I think he is asking how many accounts objects that can be created, not how many people can be using the system at once. –  Zoredache Sep 28 '11 at 22:08
    
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closed as off topic by joeqwerty, mailq, Iain, Ward, GregD Sep 28 '11 at 21:10

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4 Answers

2^30, or 1,073,741,824.

Reference here - it refers to Active Directory, but the user's ID in the local store is assigned a RID in the same way as in AD.

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I highly doubt Win 7 uses the AD layout for this. More likely the SAM database from NT4 days –  uSlackr Sep 28 '11 at 21:07
    
@uSlackr Ask your local user store. You will get an active directory-style SID. Give it a shot: technet.microsoft.com/en-us/library/ff730940.aspx –  Shane Madden Sep 28 '11 at 21:14
    
the RID limit would still apply, I think - the SID/RID scheme has been taken over from NT SAM security database into the AD. –  syneticon-dj Sep 28 '11 at 21:17
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The accounts are stored in the SAM, which is part of the registry (KB124594, if you really nead a reference for that). The registry however does not have any size limits beyond the maximum file size limit of the filesystem since Windows XP - see KB292726. So the answer would be that there is of course a limit (there always is one), but it is beyond any possible use case.

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Can probably answered by trial-and-error. Create a little PowerShell script like this (pseudo code):

for (int i = 0; i < 1000000; i++) {
    Windows.CreateUser("User"+$i);
}

Run it on a test system and see if it breaks. Make sure to have at least 1TB of free space. Increase the counter if you have more free space.

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There is no built-in limit, you can create as many of them as you want.

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I understand that, but PHB does not. Do you have a link to anything saying that? –  Präriewolf Sep 28 '11 at 20:42
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@Coyote Let's revert the question: Do you have a reference that Windows has a user account limit? –  mailq Sep 28 '11 at 20:48
    
@mailq Tried that; didn't satisfy PHB. –  Präriewolf Sep 28 '11 at 20:55
    
There may be no built-in limit, but there is a practical one. Win 7 appears to use the old SAM database technology from the WinNT4 days. WinNT had no built-in limits either, but there were lots of discussion at the time to limiting the size of the user database. Here's an idea. If your projected use is, say 150 accounts, write a script to create 200 and see what happens. –  uSlackr Sep 28 '11 at 21:06
    
WinNT had a total overall limit for the registry size since the registry was loaded into the nonpaged pool of the kernel (which was limited due to the kernel's architecture). –  syneticon-dj Sep 28 '11 at 21:31
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