HELP NT, WIN2kserver n Win2003 server

Hi Im a newbie in techrepublic. I have a problem which I know guys this is a breeze for you. My problem is Im Running Multiple Flat Forms or shall I call Servers. I have 2 Window NT both acting as PDC with there own domains and 1 windows 2000 as a workgroup server or Stand Alone server and Up coming Windows 2003 server. I would like this to be in a single Domain Network.
Scenario:
Windows 2000 as a local users and win nt’s has a serparate net users. NT’s has trust relationship with each other.

Problem:
Is this possible without re-installing or upgrading my server’s to join the mysterious Windows 2003 servers.. Please Give me Insights or suggestion on how can I do this stunts. Need a guidance from a guru of Windows…….