HP laptop won't even POST :(

I have a feeling I know what the answer's gonna be, but I'll ask anyway.

I recently purchased an HP laptop used from a guy off craigslist (I know, I know). I just wanted something cheap that I could sit in bed and browse the web on. It's an HP DV9720 with an AMD Turion 64 X2 CPU.

To make a long story short, it's suddenly refusing to boot. After I hit the power button, the blue power light will light up and the fans start up, but after 2 seconds, it turns off. 5 seconds later, it'll do the same thing all over again. It just keeps trying to boot like that until I pull the battery. I've also tried it without the battery and just running off AC power. Nothing helps though.

Any ideas? What should I start troubleshooting first? I have a feeling it's just going to be something like "the mobo's fried" and I'm SOL. I only spent $250 on it in the first place so I'm not going to ship it off to HP. Thanks in advance.

First thing I would do is test the hard drive, then hook the hard drive up to another PC and run a full virus scan with Malwarebytes. Please state the OS.

http://www.malwarebytes.org/products/malwarebytes_free