MAC filtering is anemic protection and is easily bypassed.
For your reference, here's how to
Change MAC address using Windows.
Don't count on this type of filtering to protect your network. WPA/WPA2 is the ONLY effective wireless protection. WEP is better than nothing, but is also pretty easily cracked with common tools available on the Internet.
A good read: The Six Dumbest Ways to Secure A Wireless LAN