ip, you can change if you ISP provides you witha dynamic. you can change that by logging off and back on if you're on dial-up, or by typing in cmd, ipconfig /release and ipconfig /renew or switching off your modem and turning it back on if you're on
dsl
the mac address cannot be changed for the simple fact that your NIC has a specific mac address which specifies the brand etc. it's hardcoded on the card and will not change!