Windows Server 2000 Folder Permissions to XP Pro

In the office I work in our Domain Controller is running Server 2000 (Backoffice). Its an older machine serving about 50 users. It currently is handling our data, and we want to move our data off of the main machine to a secondary box. So we setup a box with Windows XP Pro on it. The two machines can communicate and see each other, so we started copying some of our data over to the file server. (Redundant copies are everywhere). However the permissions that are given in the Server 2000 box do not transfer over to the XP box for certain files.

I can't figure out if its something we've done wrong, compatibility issues, or something totally different.

Unfortunately this office does not have an IT person on staff. I am just an 'intern' with I'd say advanced computer knowledge, and intermediate networking knowledge. The rest of us (including me) are "GIS" personnel hoping and trying to manage our data.

Any ideas/thoughts would be helpful.