INspiron 5100 New Hard Drive

Yes. Look at the back of the original drive. You need to remove the edge connector from it and place it over the pins on the new one. Until that's done, the drive is not connected to the mainboard.

I believe this drive already came with the edge connector attached.  Visibly, the two drives look identical.  What else could it be? Thanks!

The chances of a new drive being defective are low, but it does happen. If you have another system, test the drive in that - if it works, the problem is with the mainboard, not the drive.

I do not have another system.  Any other suggestions?  The whole reason I bought a new HDD was that I got a blue screen error telling me that windows was shutting down and dumping physical memory due to a hardware issue.  I could not even get it to reboot......When I pressed the power button, the fans would kick on, it would begin to start up, and then just shut down.   I figured it was a prob with the HDD, so I purchased a new one.  However, after receiving the new one, I tried to install it, and after booting, it gave me the same error message.  Took it in to a local repair shop, and they told me that my RAM had come loose.  They apparently put it back in, and now I can start up the system, but for whatever reason it does not recognize the HDD.  This is soooooo frustrating.  I F12'd and the diagnostics says there is no drive present.  Hope someone can help!!!

Given the other symptoms, I'd say you replaced the wrong part - it's the system board that is failing, not the hard drive.

But why will it read the old hard drive and then lock up at random times, and not even read the new hard drive at all?