Computer won't detect second HDD

[dhdarren]

Hi! I have an HP desktop on W8.1 that came 3.5" 1TB HDD. We had an older laptop that died which had a 250GB HDD. I tried to plug in the laptop hard drive into my desktop, and when the 1TB HDD is NOT connected, it boots fine in W7. However, when the 1TB HDD IS connected, the computer won't even detect the other hard drive. Could it be because they both have an OS installed on the hard drives? Thanks so much!

 

[SuperSoph_WD]

Hey there, dhdarren!

I'd suggest to take look in the BIOS and see if the HDD is enabled there.
Check if it shows in Disk management and see its status there:
http://pcsupport.about.com/od/windows7/ht/disk-management-windows-7.htm
If it shows there, you should re-format it which would result in losing all data on your old drive.
If it doesn't show up, it might be damaged or it might has corrupt data/bad sectors.

Keep me posted, so I'd assist you further with the troubleshooting.
Good luck!
SuperSoph_WD