Welcome, just a few questions,
How old is your wii, when did you buy it, did you buy it off a mate. All ?
Also its better to use this site:
www.hackmii.com
that can install DVDX.
Just click this link: "http://bootmii.org/get.php?file=hackmii_installer_v0.6.zip&key=5b19ce70423baffad56dc870bdb6c566e98af244" Unzip it, put it on your SD card,
Also im asuming you already have HBC (Homebrew Channel)
if not Follow my Guide in my Sig it works for 4./4.1 i will update it later to work with 4.2.
Also do not be affraid if your on 4.2 as its still hackable as 4.1 and the rest, Just do not Downgrade it to past 3.4 otherwise your full brick. Depending on some hardware, its a gamble if you want to downgrade below with the latest updates.
Anyways have fun, need anymore info just pm or post.