most wii bricks where the wii wont turn on are a result of uninstalling the SM, SM IOS, or installing a stub SM IOS (or installing a SM for the wrong region). There may be other ways too (like buggy boot2 update), but those are the basics
get him to try accessing bootmii and/or priiloader, if he can't access that then u only have 2 options left
1) if he has nand backup and/or keys, u can use an infectus mod chip to flash his nand
2) send it to ninty for repairs
edit: no game has the 4.2 update on it yet, New Super Mario Brothers Wii has the 4.1 update (and i think it also has a boot2 update, not sure) which the most recent update found on disc (as for as i know)