1. 在 HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}\0000、0001、0002等主鍵下，查找DriverDesc，內容為你要修改的網卡的描述，如“Realtek RTL8029(AS)-based PCI Ethernet Adapter”。
2. 如果在0001下找到了1中的DriverDesc,在其下，添加一個字符串，命名為NetworkAddress，其值設為你要的MAC地址（注意地址還是連續寫）。如：00E0DDE0E0E0。
3. 然后到其下Ndi\params中添加一項名為NetworkAddress的主鍵，在該主鍵下添加名為default的字符串，其值是你要設的MAC地址，要連續寫，如：000000000000。（實際上這只是設置在后面提到的高級屬性中的“初始值”，實際使用的MAC地址還是取決于在第2點中提到的NetworkAddress參數，這個參數一旦設置后，以后高級屬性中的值就是NetworkAddress給出的值而非default給出的了。）
4. 在NetworkAddress的主鍵下繼續添加名為ParamDesc的字符串，其作用為指定NetworkAddress主鍵的描述，其值可自己命名，如“Network Address”，這樣在網卡的高級屬性中就會出現Network Address選項，就是你剛在注冊表中加的新項NetworkAddress，以后只要在此修改MAC地址就可以了。繼續添加名為Optional的字符串，其值設為“1”，則以后當你在網卡的高級屬性中選擇Network Address項時，右邊會出現“不存在”選項。
5. 重新啟動你的計算機，打開網絡鄰居的屬性，雙擊相應網卡項會發現有一個Network Address的高級設置項，可以用來直接修改MAC地址或恢復原來的地址(選中不存在)。

For Windows 2000/XP

Method 1:
This is depending on the type of Network Interface Card (NIC) you have. If you have a card that doesn’t support Clone MAC address, then you have to go to second method.
a) Go to Start->Settings->Control Panel and double click on Network and Dial-up Connections.
b) Right click on the NIC you want to change the MAC address and click on properties.
c) Under "General" tab, click on the "Configure" button
d) Click on "Advanced" tab
e) Under "Property section", you should see an item called "Network Address" or "Locally Administered Address", click on it.
f) On the right side, under "Value", type in the New MAC address you want to assign to your NIC. Usually this value is entered without the "-" between the MAC address numbers.
g) Goto command prompt and type in "ipconfig /all" or "net config rdr" to verify the changes. If the changes are not materialized, then use the second method.
h) If successful, reboot your system.

Method 2:
This should work on all Windows 2000/XP systems
a) Go to Start -> Run, type "regedt32" to start registry editor. Do not use "Regedit".
b) Go to "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002BE10318}". Double click on it to expand the tree. The subkeys are 4-digit numbers, which represent particular network adapters. You should see it starts with 0000, then 0001, 0002, 0003 and so on.
c) Find the interface you want by searching for the proper "DriverDesc" key.
d) Edit, or add, the string key "NetworkAddress" (has the data type "REG_SZ") to contain the new MAC address.
e) Disable then re-enable the network interface that you changed (or reboot the system).

Method 3:
Use the program Etherchange from http://ntsecurity.nu/toolbox/etherchange/