It seems that everyone is way ahead of me in retiring Windows XP computers.  Yet, I didn't see any messages posted suggesting ways to find Windows XP computers on a local network.  I recently recalled that one of the attributes for computer objects stored in Active Directory is operatingSystem.  I verified that the attribute was populated and wrote the following query:

dsquery * dc=knet,dc=kbs,dc=msu,dc=edu -limit 0 -filter "(&(objectClass=Computer)(operatingSystem=*XP*))" -attr cn operatingSystem distinguishedName

The default limit is 100, and if the count is higher than 100 because you have computer objects for computers that have been retired like I do, you might need to specify an override for the default limit.

Since most administrators probably have fewer active Windows XP computers in their domain than we have in ours, the above query is probably not particularly useful in building your list of Windows XP computers.  However, it could be useful in removing XP computer objects from your Active Directory.

DSQUERY seems to be included with Windows Server 2003 and higher.  Windows Server 2003 Support Tools can be installed on Windows XP to get DSQUERY on Windows XP.  On Windows 7 I think you need to turn on the feature "AD DS Snap-ins and Command-line Tools" in "Programs and Features" (appwiz.cpl control panel) "Turn Windows features on or off" under Remote Server Administration Tools » Role Administration Tools » AD DS and AD LDS Tools.

DSRM removes active directory objects identified by distinguished name.  Unlike dsget, dsadd, dsmod or dsquery, it does not use the qualifiers "computer" "user" or "group".

If you edit your list of XP computers retrieved from Active Directory and save the distinguished names of all the retired XP computers to a text file, you can remove them from Active Directory with a command like the following:

dsrm -noprompt < distinguishedNamesOfRetiredXPcomputers.txt

I wasn't sure that I trusted Active Directory to have correct information for the operatingSystem attribute, so I checked some computers that were upgraded from Windows XP or Windows Vista to Windows 7.  It looks like under normal circumstances the operatingSystem attribute is updated when a computer is joined to a domain.