How can I obtain the MAC Address with C? (in Linux and in Windows)
and how could I change it?

Hmm...
I could change my MAC Address in Linux typing this:
Code:
ifconfig eth0 down hw ether ff:ff:ff:ff:ff:f0
and then I'm gonnna need to up the new MAC Address:
Code:
ifconfig eth0 up
In windows, the MAC Address is in the registry:
Code:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlClass{4D36E972-E325-11CE-BFC1-08002bE10318}
Then search for NetworkAddress (it's in the 0009 directory)

Thanks in advance.