[You must be registered and logged in to see this link.]Did you download from one of the links on this page ?
If you did the most likely things to try are: check you're antivirus and windows defender etc aren't blocking any part of the files, run as compatible with windows service pack 3, run as administrator etc.
If you are running it on windows 8.1 you will have never ending problems.
If you've gone through the list and still have trouble getting on let me know and i'll upload a working client with dropbox.