I have a problem I have written a program with c# that it should change MAC-address but windows says I can set MAC-addresses that start with 02 or 06 or 0A or 0E What should I do? Can I disable that permission?
The short answer is that you can't because certain values are reserved, in much the same way as certain IP addresses have reserved meanings.
The problem you are encountering is that there is a difference between local and universal MAC addresses.
The format of MAC addresses is defined by the the IEE 802 Standard. Windows, or C# are almost certainly enforcing the standard, although you don't say what method you are using to attempt the change.
For a diagram of MAC address layout, please see: IEEE 802 layout
