NT4 to W2K upgrade

At the moment we have different DHCP scopes setup on our domains, so for example on one domain we have a scope so that 1.0.0.1 ? 1.0.0.50 are reserved and all other addresses area available ? what happens to these scopes when upgrading to Active Directory? We are planning on changing our existing domains to Organisational Units (OUs) ? can scopes be setup within OUs? Please advise.