This is a bit advanced for most users but it is possible to "fake" your IP or at least spoof it by changing the MAC address that is built into your ethernet adapter.
Make sure you read it all before trying this and you should have some knowledge of using the command program in NT/XP so you can reset your IP config if anything goes wrong. It's not hard to learn, just take your time and be sure to understand the concepts. I've done this hourly, daily, it doesn't matter how often you change. If anything goes wrong, usually disabling your network adapter, reboot, enable adapter, then another reboot = DHCP should correct things.
Backup your DNS settings, registry, and copy IPCONFIG before you start anyway!
(look at the bottom of the page for other systems)
downloads are just below this >Before we start:* KLC Consulting Security Team has developed a Windows MAC Address Modifying tool, SMAC.* SMAC is developed based on this research article, and it has many functionalities.* SMAC allows Windows 2000, XP, and 2003 Server users to change MAC address regardless of whether manufacturers allow this option or not.* URL of SMAC is http://www.klcconsulting.net/smac.
" SMAC must be used for LEGAL and ETHICAL purposes ONLY. "