I have just fitted a new HDD. I screwed it into the place for hard drives, and to the motherboard and power supply, using the existing power/SATA connectors left over from the hard drive I had to remove some time back, due to overheating.
The computer has not reacted to the new drive at all. From memory you usually get a pop up from the notification area "Found New Hardware', this has not happened.
Also, when I go into disk management to format the new drive the new drive does not appear.
I thought I knew what I was doing when it came to fitting new hard drives, having done it more than once, but this is a new conundrum for me.
How can I get the computer to "see" the new drive?

Boot into your BIOS Setup Menu and see if you can see the drive in there.

Check your jumper settings on all hard drives in your computer.

Make sure they don't interfere with eachother,

Hope this helps.

Roy

Hi, and thanks to Royski and Digerati.
I am slightly embarrassed to report that the new drive was not connected to the power supply. In the period since the old drive was removed, and the new one installed I also had to replace my power supply. The friend who did this more for me did not connect the power supply to a socket that was going nowhere.
Yesterday I took the side off the box to see if I could feel any vibration from the new drive, which would indicate that it was spinning, While I was doing that I checked that the SATA cable was connected to the motherboard, it was; and that the new drive was getting power, it wasn't. But it is now, so problem solved,
One interesting thing that means little but I thought I would share is that on starting the machine the BIOS spotted the new drive, that gave me a real lift. Then Windows started, I clicked on my user name and all that happened was I saw the picture on the desktop; no taskbar, and no icons! I was a bit perplexed and switched off in order to make an appointment. When I got back home I started the machine and got my normal desktop. So I formatted and partitioned the new drive, and have just finished copying files from the old drive.
Alls well that ends well. Thanks again for the suggestions, they were on the right track.

I am slightly embarrassed to report that the new drive was not connected to the power supply.

LOL - Well, rest assured, you are not the first.

Glad you got it sorted out and thanks for the followup.