System : Win 7 64bit
I was having the same problem - XAMPP was working fine one day, and then just packed up - Apache would not run and the control panel just went sulky.
After a lot of digging around, it would seem that the problem (in my case) was that ports 80 and 443 were being used. As it turns out, by Microsoft IIS. Which I have never used, and certainly have not knowingly installed...
Solution :- Control Panel --> Programs and Features --> Turn Windows Features on or off You should find "Internet Information Services" there - just untick the box and press 'OK'. Restart your computer and you should be up and running ...
Hope this helps!