My planned build

[Ualaa]

If you run the "Repair" utility, warcraft will update the registry for its new home on the computer.

Can safely copy/paste from another drive, or even a flash drive. And then "repair" warcraft, so the registry points to the new location. Which is good for patches, especially if you're not in the expected default directory.

[Tim]

I actually run the repair from time-to-time and it feels like it helps.

I think also if you just copy it over, running Launcher for the first time will also set the proper registry keys for doing updating. If those keys already exist, Launcher won't modify them, but just like Ualaa said, Repair will.