[Resolved] htc mozart 7 bootloader topic

hi guyz!!!!!
i just have bought this phone htc mozart 7 and i dont like its win 7.5 therefore i have decieded to install custom rom like win 7.8 in it but when i open bootloader i gives me three colour screen blue red and white on the top of the screen it says security unlock and in the end it gives serial
plz tell me how to unlock its bootloader or how to go forward :crying:
plz help !! thnks in advance