I just got a new computer; raids at full graphics with 60 fps, yay! And discovered that WoW is a real pain to install clean from original media. The easiest official way is to download a 3.5 gig installer for 2.0, then download another gig of patches you have to download. And it's all from Blizzard's awful bittorrent downloader that gobbles up all your bandwidth. No thanks.
Fortunately there's an easier way; just copy your old install to the new computer. The entire World of Warcraft directory. There's no registry settings or hidden other things that matter, it's all in the one directory. I moved an install from WinXP to Vista64 with no troubles. As a bonus I kept all my configuration settings and addons.
That same convenience also means Blizzard's code is incompatible with Vista's UAC security. Vista doesn't want programs writing stuff into Program Files. The easy solution is to install WoW in some other nonprotected directory, I chose C:\Games.