I was wondering how can I enbable the DHCP server in windows-vista and how can I change the ip address in the DHCP server?
There is no DHCP server included in Vista. If you need one, you will need to download it somewhere else (like DHCP Turbo).
Only situation where DHCP server does come out-of-box is if you use Internet Connection Sharing. That will change your IP to 192.168.0.1 and handle DHCP for all clients that do connect. However, your IP must be 192.168.0.1 and you cannot control DHCP range it gives away.