I would like to design the LAN environment for my company.

My company' IT environment is described as the following :

1. has three storeys
2. each storey uses Cisco 2950 Switches.
2. every storey is an individual VLAN
3. W2K Server as the LAN DNS
4. WinXP as the clients for Desktop, laptop and notebook computer

The requirements :

How can I configure a DHCP server for all users
( all client computers get IP address which belong to their storey ) ?

The only DNS Server has to register all users from all storeys ?

Can I use the Exchange instant message for all users in the storeys ?

How to achieve the above goals ?

Thank you for your help