Welcome and hopefully i can help you resolve this issue
Im assuming Windows 7 64bit is the operating system on your machine?
Do you have the Windows 7 disc also?
Firstly i suggest you boot in to the Advanced Boot Options screen by pressing F8 continuously at the Asus splash screen and select Last known Good configuration. If that doesnt work select Disable Automatic Restart on System Failure and reboot your computer.
If you get a BSOD (Blue screen of death) upon reboot, like the one below, look up the stop code similar to the one here and post the code back.