I found this, I hope it will help you :
Alienware 13 R2, 15 R2 and 17 R3: 7 Beeps | Dell UK
My Alienware 17 R2 Beeps 7 Times But When I Press Power It stop beeping and remains on but no POST or screen even on external monitor???
I have tried everything even the blanket thing (lol) wrappin g it up but i only did that once..
Any ideas will be GREATLY appreciated!
I really don't have the money to get a new board but i am very tech savvy though..
Please help me!!!