Ok, used Regmon to figure out where TweakUI was setting a registry key. I've never made a custom .adm before, and wanted someone to make sure I did it right 
There's no info I can find about these keys except through TweakUI. This is using XP's TweakUI, and I don't have a 2k machine to try it out on. Any insights would be appreciated 
CLASS MACHINE
CATEGORY !!System
CATEGORY !!Logon
POLICY !!ShowDnsNames
EXPLAIN !!Dns_Explain
VALUENAME "DCacheShowDnsNames"
VALUEON 1
VALUEOFF 0
KEYNAME "Software\Microsoft\Windows NT\CurrentVersion\WinLogon"
END POLICY
POLICY !!ShowDomainTags
EXPLAIN !!Tag_Explain
VALUENAME "DCacheShowDomainTags"
VALUEON 1
VALUEOFF 0
KEYNAME "Software\Microsoft\Windows NT\CurrentVersion\WinLogon"
END POLICY
END CATEGORY
END CATEGORY
[strings]
ShowDnsNames="Show full DNS domain names at logon"
Dns_Explain="If this policy is enabled, the list of domains at logon will show full DNS names. If it is disabled or not configured, NetBIOS names will be shown."
ShowDomainTags="Show additional domain information at logon"
Tag_Explain="If this policy is enabled, then the list of domains on the logon dialog will contain brief information about each domain after the domain name."
System="System"
Logon="Logon"