Just as a test, assuming you can boot to the PS3's XMB, go to the PSN Store and download a game demo or some kind of movie trailer. Doesn't really matter what, just pick the smallest thing you can find, download it, and see if that works.
If it does, then odds are it's your bluray drive that crapped out. If it doesn't, it might well be your hard drive, in which case you can easily swap it out with another. The PS3 just uses your basic 2.5" laptop drives (SATA) so you could go out and buy another to swap in.
If it is your bluray drive that died, or it's something else that's wrong, you have two choices. First is that Sony has a program, where for about $150 they will repair a PS3 to working status again regardless of what's wrong. Or you could go out and buy a new PS3 Slim, which would have the added benefit of consuming less power (about 33% less by most reports). You could sell your old on ebay to help offset the costs a little more, and then know that over time, the slim PS3's lowered power consumption will save you money on electricity bills. Thus paying for itself over time, and possibly even saving you some money long term.
I'm having a little trouble with my PS3. I put the disc in, but it doesn't seem to load. I typically would hear the hard drive start to spin, but I'm not hearing that anymore. It worked just fine yesterday, and now today, nothing. Usually when I put the disc in and hit the PS button on the remote a little circle in the upper right screen will start spinning, but now I just get a blank screen..nothing! Does anyone have any advice as to what the problem may be? I'm thinking my hard drive might be fried, but I've only had it for a little over a year and don't think that it would fry that quick.

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