Why doesn't my computer see my hard drive

Is that drive new? It sounds like the drive is taking longer to spin up than the BIOS takes to check the installed hardware. First make sure the power cable is connected well, and that there are no adapters which can sometimes cause power issues.

If the above is good then go into the BIOS and see if there is a setting that says something like "fast boot", or "fast hardware check", or "fast memory check", and say no so that the BIOS will take longer before it looks for the hard drive.

The drive is 6 mo. old originally had no problem with it. I just went in to my bios after a shut down and I could not find anything about fast boot. BUT I noticed that hard drive was not in the list of boot order.
I have changed the battery as well.
Some additional info may help. My pc only has 1 drive. I changed the cable so I could put 2 grives in and copy from 1 to the other. It recognized both drives immediately. It was after that I went back to 1 drive it would not recognize the drive. I have tried both cables and receive the same response so it is not the cable. This is aggravating.
Thanks again Bill

It sounds like these are IDE drives. Did you have to move jumpers for master/slave when you added the second drive? If so, did you restore the jumper to it's original position after you removed the second drive?

yes I tried both master and CS

Does the drive have a single setting? On most drives, I think it's with no jumper installed at all. There should be a pin diagram on the face of the drive that shows all the settings.

When it was working it was in the CS mode which it is set to now. I don't recall seeing a no jumper setting
Thanks Bill