I bought a used laptop from cowboom. It's a Dell Inspiron 3520 that's supposed to have a Windows 8 key. Anyway, immediately when I loaded it up, it said "no internal hard drive found." There' supposed to be a 500GB Toshiba, and it's actually listed in the Bios main. I opened up the computer and it looks like it was inserted properly. Just in case, I unplugged it and reinserted it and... same thing. I also tried this spare 120 GB Toshiba I had lying around and the same problem. It appeared in BIOS, but no internal hard drive found on bootup. Any ideas about what's wrong?