/shared2/sys/SYSCONF
The SYSCONF contains many Wii system settings.
The format of the file is fairly simple. Its size is 0x4000, and tt contains a header that reads "SCv0", followed by the number of settings in the file (u16), and then a list of offsets of each setting (u16). Each setting contains first a type identifier (u8), then a name (char*), and a value (varies, based on type). libogc/marcan's conf.c contains code to parse this information.
Conventions for adding or removing settings to the file are currently unknown, but shouldn't be too hard to determine--although that's not necessarily a useful function.
Types Template:Table Template:Table/Header Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row |}
Some settings from the file:
BT Settings Template:Table Template:Table/Header Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row |}
IPL Settings Template:Table Template:Table/Header Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row Template:Table/Row |}
IPL.SADR values: Offset 0 is a Country Code and offset 1 seems to be a more localized region code.