Having played WoW for about 5 years, yes copying does the job fine. My own copy of WoW has come from Windows XP to Windows 7 64-bit. I would advise putting it in a folder such as C:\Games\ instead of C:\Program Files (x86)\ otherwise UAC could get a bit messy in how the addon data gets saved there. If that doesn't work out for some strange reason, use the WOTLK DVD to install WoW from scratch (note you don't even need to install Classic or Burning Crusade discs first) and then copy over the WTF and Interface folders to your new location.
