I am assembling a new rig and can't enter the BIOS setup screen.

For initial testing, I have assembled the following components on a piece of cardboard (I have other HDDs and optical drives that I intend on installing later):

Asus P5LD2 Deluxe motherboard
Intel P4 650 3.4MHZ cpu with heatsink and fan
2x1024MHz OCZ DDR2 667MHz Gold Edition memory sticks
WD 2500KS 250GB SATA2 HDD
MSI NX7800GTX PCI Express Video card
Enermax Liberty 500W psu
Monitor
Keyboard

First I turn on the monitor, then the power (I was able to connect the case power and speaker wires to the motherboard).

This is what I hear/see:

1. Single beep.

2. IT8211 ATAPI BIOS V1.3.1.61
Copyright 2002-2004 ITE, Inc. All Rights Reserved.

Please wait for IDE scan.

3. IT8211 ATAPI BIOS V1.3.1.61
Copyright 2002-2004 ITE, Inc. All Rights Reserved.

Drive 0: Not Detected.
Drive 1: Not Detected.
Drive 2: Not Detected.
Drive 3: Not Detected.

4. SiI 3132 SATALink BIOS Version 7.2.18
Copyright 1997-2005 Silicon Image, Inc.

5. Single beep.

6. Flashing cursor for about 5 seconds.

7. Reboot and Select proper Boot Device
or Insert Boot Media in selected Boot Device and press any key.

I can't go any further.

Also, sometimes when I go through this process, the first thing that appears on the monitor is an image that says Asus P5LD2 Deluxe, but it only lasts for maybe 2 seconds. And sometimes during the above display, I see a brief message that says "Keyboard not detected", and something about Cheksum. It goes by so quickly that I can't read all of it.

Anyways, there it is. Does anyone have any idea what is going on here, and why I can't get into the BIOS?

Have you tried to get into bios? Just checking, as you didn't mention anywhere above that you pressed the del key (it varies from bios to bios but I believe it is the del key for your motherboard).

Immediately after you hear the beep, tap your del key a few times and let us know how it goes.

You may want to clear your CMOS too, (read your manual on how to do this, but it involves moving the jumpers for a few seconds) as this may solve your checksum error.

Are the lights on your keyboard lighting up? Is it USB or PS/2? Try with PS/2 if you have it connected via USB (assuming USB isn't working).

1. Yes, I have pressed Del to get into the BIOS.
2. I cleared the CMOS as per the mobo manual instructions.
3. I pressed Del immediately after the first beep, and the same thing happened.
4. My keyboard lights are not on. I have a P/S2 connection.

Read your manual on how to enter bios. It is usually the del key but could be one of your F keys as well.

But it sounds to me like your keyboard is not working, which may be your problem... The PS/2 connection isn't working you say? Can you try it with a USB connection? Do you by chance have another keyboard you can use to help troubleshoot?

Well... I discovered that one of the pins on the connector of the keyboard cable was missing. I replaced the keyboard and am now able to go into the BIOS. Also, the lights now work on the keyboard, as they should.

Thanks for the suggestion.

This is a prime example of how troubleshooting should work. You noticed a keyboard remark, checked your keyboard and found a pin missing.
Case closed. All troubleshooting should be so easy, lol.