1. Clearing the CMOS requires that you open up the computer case and directly work with the PC's internal components.

2. If proper the proper steps are not taken you could end up hurting yourself (via electric shock) and shorting your motherboard (via your static electrcity).

3. If you chose to clear the CMOS, discharge any static electricity that you may be carrying around. The simplest way of doing so is to wash your hands. Some manufacturers also make static electricity discharging wrist straps if those interest you at all (although I don't think the straps are worth using).

4. While it's not required, it's generally not a good idea to proceed with any CMOS clearing activities while you or your PC are on a carpeted surface.

5. Sometimes, in order to gain access to the CMOS battery or jumper (mentioned later), you'll need to move some wires/cables out of the way or in extreme cases like mine, remove the entire VGA card.

6. I'm not responsible for anything that may go wrong during or as a result of the CMOS clearing procedure.

1. Power down your PC.

2. Unplug the main power cable from the back of your power supply as well as any other wires/cables that are keeping the PC from being easily accessible.

3. Press the power button as if you were booting your computer (in order to dissipate any residual power).

4. Crack open the computer case (via hinged door, removable side panel, or otherwise) and lie the case on its side (if helpful).

5. Unplug the 24-pin main power connector from the motherboard.

6. You have the options of doing 6a or 6b, but I like to do them both.

(a) Locate the CMOS jumper on your motherboard (it generally has 3 pins and is located near the CMOS battery) and move the plastic tab from pins #1 & #2 to pins #2 & #3 for about a minute, then move the tab back to its original location. The CMOS jumper and battery look something like this.
Note: Not all motherboards have a CMOS jumper.

(b) Locate the CMOS battery on your motherboard and remove it (if applicable) for about a minute, then press the battery back into its original location.
Note: Some CMOS batteries are soldered to the motherboard and cannot be removed.

7. Reconnect the 24-pin main power connector to the motherboard.

8. Close up the case, reconnect the main power cord to the PSU, reconnect any other miscellaneous wires/cables you may have unplugged, reboot the computer and attempt to enter the BIOS.

Hopefully you'll be able re-enter the BIOS after all of that is done (should you choose to do it). If you are able, or even if you aren't I suppose, your BIOS should have been reset to its factory defaults and you'll want to be sure to change the system date/time to its present value (it normally resets to some date/time like 01/01/2001 00:00:00 or something like that). After resetting that information, I would:

1. Browse though the BIOS and try to disable the FDC.

2. Change the boot sequence (as dubbed by my BIOS) so that your internal HDD(s) boot before anything else.

3. Ensure that an option called "USB Legacy Support" is enabled, should it exist in your BIOS.

4. Continue to browse though the BIOS and enable/disable options as needed (if you know what you're doing).

5. Assuming everything has started working again, flashing your BIOS to a newer version wouldn't be a bad idea. Flashing the BIOS resets factory default settings in the BIOS too, I believe.