To brick a Wii is to damage the console beyond repair - as in 'A bricked Wii has all the electronic functionality of a brick'. To put it simply, fully bricked Wii consoles do absolutely nothing. The term is often used in situations where modifying a system's firmware (without necessarily making any alterations to the machine's hardware) has caused it to become inoperable.
A “full-brick" Wii displays an Opera error message instead of the “warning” screen when the Wii boots — it does not even check the disc drive for a disc before displaying this, meaning it is impossible to fix this using software unless you use a Savemii with an autoboot disc.
Full bricks due to other causes can simply cause black screens on boot. Some are recoverable with a SaveMii and an autoboot disc, and others aren't.
A semi-bricked Wii has a small error in the System Menu. Once a Wii is semi-bricked, it cannot enter the settings screen. There are repair discs for semi-bricked Wii consoles, but not for those fully bricked.
Why it Bricks
Each region has its own version of the System Menu (1-2). For example, 3.2 of the System Menu available is v. 288 (NTSC/J), v.289 (NTSC/U), v.290 (PAL). The only difference between those three versions is two different files — the main executable for the menu (a .DOL file, more or less) and an ARC archive that stores compressed versions of the HTML / image resources.
All of this is fine and good, but why put them in separately named directories? (E.g. EU/EU/GER/Setup/ScreenSave.html above)? The path name could always be the same because there are different files for each version.
So, there’s a specific path that the graphics need to sit at. So, you’d think they’d hard-code a pathname like that into the code, right? No…
The code’s pretty hard to tease apart, but they seem to be trying to determine the system region from the setting.txt file, and then building up a pathname to load like so: sprintf(filename, “html/%s2/iplsetting.ash/%s/%s/ENG/Setup/ScreenSave.html”, region, region, region). This is so silly, because if they had hard-coded the path then the system would have booted just fine.
A full brick is caused when SYSCONF is missing, damaged, or has the "reconfiguration" flag set. This usually occurs after certain updates. The Wii would usually show the settings screen on boot to let you adjust some settings, but since it is broken, you end up with an un-bootable Wii.
- Only install updates for your own region.
- Play your own region. Generally, playing games or using Wii Menu channels from other regions shouldn't cause any problems, but in exceptional circumstances something could go wrong. (Note that games and channels from other regions will not function without modification.)
- DO NOT delete critical system files.
- DO NOT install modified versions of system files, unless you have a very good reason to do so.
- DO NOT install unofficial channels unless they come from a trusted source and really serve a useful function. Malformed channels (especially the banner part) can make your System Menu crash on boot. Loading applications from SD is much safer.
- Ensure that you know what you are doing when installing/running homebrew applications, especially those with the "Homebrew Dangerous if Misused" banner on their page.
- Be VERY careful with applications such as AnyRegion Changer, Starfall, downgraders and any other applications which obviously mess about with the system files.
- Don't touch your Wii's power or power button while doing any updating or installation of system content. Definitely don't do those during an electrical storm.