How do you change command and conquer the first decade serial number

Go to start menu type regedit
Find the following entry
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Westwood
Under there on the left hand side you should see listed the games you installed such as Red Alert II or Yuri's Revenge ETC
Click the Folder on the left column of game you want to change the serial number of
Then under each game is an entry on the right hand side saying serial, right click this and go to modify, a box comes up allowing you to change the serial.
No spaces are needed for the serial.