2011 Macbook Pro not well

[Shed209]

I have a 2011 Macbook pro here, that I bought second hand with a fault that seemed as though it might be a faulty hard drive. However, having bought a hard drive for it, it's still not cooperating. I start the internet recovery process, and get past the stage of logging onto my wireless network and doing the initial file download. Then I get the apple icon with a little circle thing under it, but then the screen goes black for a moment, comes back on plan grey with nothing else on it, and the fans start to spin up.

Any ideas what could be going on here?

Thanks in advance.