One of my hard drives stopped working I think

So I'm not sure, but I think that overnight, one of my hard drives stopped working..... I checked in the BIOS in the boot order menu, and I notice that only one drive is recognized..not only that, but now I can't even boot into windows because of this. What should I do? I have a lot of files on that other drive including my game files and stuff, I used it as kind of a backup drive since my C drive is pretty weak when it comes to storage, my other drive is 1TB I have no other backups. I'm thinking of possibly taking my computer to a shop so they can do data recovery or something... I dunno what's going on. All I know is that one of my programs stopped working overnight, and then I checked Computer, and I noticed one of my drives was missing... So I definitely think that the main drive is ok...what I don't get is how could I not boot into Windows then? It was fine before, now all of a sudden this. I'm distraught.

If you are sure BIOS boot order is correct, then possibly your boot files are in the failed drive.

Start with Windows 7 System Repair cd, and perform startup repair (may need to do it three times with reboots in between) Startup Repair

Currently it's in a shop, so they're going to be taking a look at it. I'll update when I get it back.

So the guy working on it in the shop got back to me, and apparently I guess I had a partial install of windows 8.1 on there too, and I guess the bootloader interfered with Windows 7 so it wasn't able to boot to it because of that. My hard drives are actually fine, he's just going to reload Windows 7 on my machine. So everything should be good.