Thanks for your help. I really appreciate it.
On my computer, I have three pins, instead of two, for both the password connector and the CMOS jumper. I tried several methods to reset the BIOS to default values. in all cases, I turned off the power, moved the jumpers, turned the power back on for at lease 10 seconds, turned the power off, moved the jumpers back to their original positions, turned the power back on, pressed F2 on the Dell logo screen. The system displayed "Entering BIOS Setup" but did not enter BIOS Setup. Below are the different thing that I did.
1. I moved both jumpers from pins 1 and 2 to pins 2 and 3, turned on the power for 10 seconds, turned the power off and reset both jumpers to pins 1 and 2.
2. I removed the password connector and used it to jump the CMOS jumper.
a. placed the jumper from the password connector on CMOS pins 1 and 2, turned power on for 10 seconds, etc.
b. placed the jumper from the password connector on CMOS pins 2 and 3, turned power on for 10 seconds, etc.
Again, when I booted the computer and pressed F2 on the Dell logo screen, "Entering BIOS Setup" was displayed but the system did not go to BIOS setup. Instead, "AHCI BIOS not installed" was displayed and the only way out of that was to Power Off.
Note: I mentioned that I have two identical computers except for the hard drive. When I boot the other computer and press F2 Setup on the Dell logo screen. "Entering BIOS Setup", "AHCI BIOS not installed" flashes very briefly on the screen and the system then goes into BIOS Setup.