Windows boot problem

Hello,
I've installed windows 7, all good since i restarted the windows after instalation is done. And after that , windows dont start. Shows me "welcome, setup is preparing to use windows for the first time" , then is rebooting and do this every time, i can not boot from cd also. Can somebody pleasehelp me? My laptop is a acer aspire 5520g. Please is very urgent!