Domain Controllers allow you to manage users centrally. This can be a very significant thing, especially if you have remote users ...and remote can mean just a few rooms away not just in another building ir another city. Running between machines can be a pain.
BUT - you really need to understand Win2K and user profiles and security policies etc to get the most out of this.
Problems - there can be many if you get things wrong. The worst (even if everything is working OK) is when you allow users to have a lot of control over their desktop.....this gets included in the user profile and is downloaded when they log on and uploaded when they logoff. I have seen users with nearly a Gb of profile and they can take 10 minutes to logon over a VPN.
Basically, you need to assess how many people need roaming profiles before you decide to implement it. You may be surprised how few need that....maybe none!
If you do go down the roaming profiles path, make the profiles Mandatory so they can't change them (Remember, this is a WORK PC not their home toy) to keep the profile size down. (You can seet a max profile size but if they exceed it, they can't logoff until they reduce it and what user knows how to do that?)
There is a good link on Win2k Server stuff (which is what SAMBA is emulating) at
http://www.windowsitpro.com/windowsnt20002003faq/Cheers - and good luck.javascript:emoticon('

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Very Happy
Ian