Well.. had wow installed to C:\Programs\World of Warcraft\
I have six instances of wow symlinked off of the main install.
One instance is for everything on when I one-box in raids.
Five instances is for everything turned down when I five box.

I'm running Windows Vista, Home Premium, 64-bit.
Q6600, 8gb ram, HD4870X2.
Warcraft is on the administrator account and is run as an administrator.

Prior to the 2.x to 3.x patch, immediately prior to WotLK, each patch was done by patching the main copy.
And then copy/pasting the wow.exe to each of the symlinked folders.
With that big patch, I received a red error message at the log on screen (where you input user/password info)
A blue poster eventually said to reinstall the game.

They recommended to reinstall to c:\users\public\games
The blue said Vista prefered the public area for writing to files, sometimes having issues in c:\programs\

This time, the patch goes ok at first.
After it patches it says it needs to repatch.
Launcher.exe eventually leads to a screen which says "Patch Aborted".
Wow.exe opens the wow has crashed what is the reason screen. With a dialogue about wow.exe version mismatch.
Repair tool downloaded 2mb, then 26.1mb and now finds wow to be fine.
After each repair, the same shit as above.

As usual, blues are useless saying reinstall.