[Lucky_star]

Its a rare case that each time you click release and renew, you will get a new address. It depends on the the Server. This generally occurs during the daytime when the service provider is busy and a lot of users are switching
on and off. In this case renewing may give you a new ip address. But in the night when the server is not that busy, clicking on renew will only give you the same address.

See if your modem supports both LAN and USB. In that case, if you disable LAN and connect using USB, you will surely get a new ip address.

Another way to get a new ip address is to boot into another operating system, Say from XP to 98 or vice versa.