Installing second internal hard drive

[nagoyankitty]

I had an Iomega external hard drive whose casing had gone bad so I took it out and hooked it up directly to a motherboard using SATA cable and the computer recognized it without issues. I was able to access everything just like it used to as a back up external HD. This was done on my friend's desktop. So I went back to my own desktop and tried the exact same thing, but when I try to boot up, I get a message saying "NTLDR is Missing". I have six SATA ports on my motherboard. Is there a priority issue? Is my computer trying to boot from the iomega one instead of my original internal drive??
My friend did not need to change any setting on his computer, all we did was hook it up and turn the computer on. What am I doing wrong??

EDIT-------------------------------------------------------------------
NEVER MIND lol I just had to plug it into sata slot 6 instead of 1 or 2...

 

[OhSnapWord]

Check the boot settings. does the computer boot normally without the drive connected? If so, then it sounds like your computer is trying to boot from the iomega drive.

 

[cboucher]

For some reason your BIOS is selecting the SATA drive as the number one priority HDD (as far as booting is concerned). Look in your BIOS under the boot options and you should be able to prioritize multiple hard drives (select the HDD you normally boot from).