Road Runner "Residential" does not offer static IP addressing.
The most likely reasons for an IP change are:
•You don't turn your PC on for longer than the DHCP lease period (usually 3.5 days) AND someone new in your area signs on and grabs your IP. If you have a router, it will hold your IP rather than the PC.
•You change your NIC.
•You have a router and change the cloned NIC MAC address to another MAC address.