wii theme help

Can someone help me fast.................I tried installing a theme to my wii (it my first time) when it get to that health and warning thing instead of it being that...........it is my custom theme but when i press a or z it says the system files are corrupted??? any suggestions?????????

Need more information. Do you have Preloader or Bootmii installed as boot2? Also, what system menu do you have, and did you patch the trucha bug into the system menu IOS if the system menu is 3.3 or higher? Finally, do you have a mod chip?

Was the theme for the right System Menu, and did you use the correct base app?