I just bought a new HDD purely for storage, not as a boot drive. It is the Samsung Spinpoint F3. When I installed it internally, my computer will not power up. The power flicks on for a moment but then dies. I then tried it in my enclosure for Sata HDD's which is connected via a USB cable. TO my surprise it worked fine through this and I managed to add it to my hard drives and format it in windows.
I then installed the drive again internally and the same problem. I have tried several different sata ports, a different sata cable, a different power cable.
The computer will power on if I unplug all other drives (2 SSD's) and leave the HDD plugged in but the drive does not spin up which is obvious due to the loud noise the spinpoint makes when it spins up.
Thanks a lot for the replies, guys. Pyree hit the nail on the head, though I discovered this through trial and error and have only just had a chance to get back to this thread.
I put the drive in another computer and it worked fine.
It ended up being a faulty 12v connector on my Antec HCP-850. If anything was plugged into it (including case fans) it would not power up. I ended up plugging in to other power ports. Its annoying because it's a reasonably expensive power supply and it's only a couple of months old. It's strange though because I'm sure I was using that port before.
Anyway, I hope this thread will help someone who has the same problem in future.