Computer Won't Start?

Alright, my computer was being weird so I decided to format it and install Windows 7 64-Bit again. So, recently after using it for awhile, it's started shutting down by itself. I noticed it said 'Express Gate Is Incomplete' now too. So I started the computer after a shut down, the monitor looked really weird then I got a blue screen saying my computer shut down to protect itself, then it did. So now I'm in Safemode With Networking.