2000 Domain Upgrade

HI,

Here is my scenario:

I have a 50 user 2k domain with one 2k domain controller. Exchange isn’t installed yet.

I will be upgrading the DC to 2k3 server and I want to know can I do the upgrade while the domain users are logged in and working?

I know the DC requires a reboot once the upgrade has taken place but will the upgrade mess with DNS and permissions for the users?

thanks