Security Identifiers in NT 4.0

You can use the Getsid.exe command-line application included in the Windows NT Resource Kit to determine the SID for a specified user account. Getsid.exe is useful for troubleshooting user authentication problems. You can't, however, change the useraccount SID with Getsid.exe. Use the getsid command as follows:

getsid \\servername accountname \\servername accountname

getsid requires two account names because part of its function is to compare the SIDs of each to determine whether they'rethe same.

Considering That A PDC can have 44,000 accounts the sid size should be close to that size per Server you install. I guess it would be based upon the type of doamin model you choose at your sight; Single, Master etc.! For additional information about the SAM size, see the following article in the Microsoft Knowledge Base:
Article ID: Q130914
Title: "Number of Users and Groups Affects SAM Size of Domain" and this SID Detail Article below:
http://www.microsoft.com/technet/win2000/dguide/chapt-10.asp

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A security identifier (SID) is a unique value of variable length used to identify a trustee. Each account has a unique SID issued by an authority, such as a Windows NT/Windows 2000 domain, and stored in a security database.
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According the snipet above I think this is not the case. The keyword in this is variable length. So when more SIDs are needed, more will be created.