I'm getting this error when I try to apply the patch "wow-13205-13287-Win-final.MPQ". I saw that Dr.Core posted the exact same problem and Newbalicious replied saying to re-copy "base-Win.MPQ" to the Data folder again, I tried this and it didn't change anything. I'm still getting the same error:
The patch "pc-game-hdfilesWow.exe" could not be applied. (MD5 mismatch: expected 0x0D3995E75EF62D7317D68FC92615DAA5, actual 0x3D4965F5549AE3017BA6CBD6E04C9CAA.)(PTCApply_BSDiff failed.) If this problem persists, you may be able to solve it by uninstalling and then reinstalling the game. If you are unable to correct this problem, please contact Blizzard Technical Support. (BNUpdate::PTCApply)
The current version of my client is 4.0.1.13205.
Edit: Sorry, I read on another page that you have to use "wow-4.2.1.2756-enUS-tools-patch.exe" and that worked.