failure in starting matlab

Hi, I had Matlab on my machine, and it was working pretty well till last night which I installed "Octave" on my machine and then Matlab doesn't starts! I uninstalled "Octave" but the problem still remained, I uninstalled Matlab (my version was 2013) and installed Matlab 2014 but the problem still is there! when I run Matlab, after a while (before it shows the command line) a message is shown which says that Matlab cannot start up, windows is trying to find the solution and if it finds it would tell me! also my Windows is 8.1 on a 64bit processor. best