your wii is soft modded
issue: Black screen occurs because a person installs incorrect theme or you have turned on the Black Screen hack on priiloader.
How I Fix: You must have priiloader or bootmii installed as boot2. You must have an SD card preferably not SDHC.
he's my hack pack which all of its contents are in this link
http://uploading.com/files/aaa42336/Microwavesam-Wii%2BHack%2BPack.rar/If you already have priiloader and mymenuify in your SD card, you do not need to download the hack pack.
Power on Wii
Hold Reset to access priiloader
Drop down to Launch Title
Drop down to Homebrew Channel and Press A
Go to Multi-mod Manager and Load it from homebrew channel
For Bootmii as boot2 if you have the folder named as bootmii on your SD card, you will automatically boot into Multi Mod Manager when you start the Wii
Go down to Manage System Menu
Attention: You must either have internet connection for this method. Press A to continue and press A again to download. After completion, press B and then Home to get out.
Press Home and exit to system menu. Your wii should work.
Alternatively, you can install NUS Downloader on the computer and download the System Menu Wad file and install the WAD with the system menu to fix the Wii.http://wiibrew.org/wiki/NUS_Downloader
Go to computer
If you know your Wii version menu and what region it is from, Search a theme on youtube or google to download a correct theme for your Wii version menu and region. For example, If you have 4.3U, search on youtube and google for 4.3U Mymenuify Theme.
Download and if so extract the contents
Copy the contents into the SD card. You can name a folder called Themes and copy the theme file in there. The theme itself is usually just one file.
Bring the SD card into the Wii and install it
Exit and press home and exit to your system menu and your Wii is working again.
if you get stuck let me know I'll put vid up to walk you though it