Q: Macbook Air hang everytime power on

Do any of you ever have experience with macbook air hanged ? This is starting happen when i click info from machintos HD and there is sharing&permissions and under "you can only read" there 3 kind of it (system, wheel, everyone), i delete everyone and wheel i set no access. since i set it like that. suddenly the mac so lag and i try to reboot it. ****, the problem is starting there. i don't mind to format it and install it all again. the problem is all the data inside i never back it up. and i need it so much please anyone expert in this ?