I had two hard drives, one was 1Tb the other was 500Gb. BIOS was always weird with recognizing which one it was booting from, but when I installed windows and looked at C:\ through windows I could see it had 1Tb free, so I knew I was running off of that one. Recently, I had to take the 500Gb out, which was empty. After taking it out, I tried to boot from the 1Tb again, and it told me to insert a boot device. It's showing up in BIOS and it's properly set as my primary boot device, but when I try to boot it doesn't work. I booted from a windows disk to see if it could see the hard drive, and not only was it recognized but I could also look through it and see that my windows files were all there. Any help would be appreciated. I apologize in advance if I'm not including obviously useful information.