Sorry I have no clue whats gone wrong. My guess is your OS is damaged in some way, but that is just a guess.
The problem will likely resolve the next time you do a clean install. At which point I suggest you start employing backup software like True Image.
Then if you run into problems you just restore from the previous backup.
If you have system restore enabled you can try recovering from a restore point before the problem occurred.
You can even go a step further and isolate your development environment by running it inside a Virtual Machine. Then you can install XAMPP in a freshly installed OS.