HELP ABOUT K8C-X motherboard

Hi thun, Unplug the power cable from the PC.
Please reset the bios. This is shown in you're user manual on page 1-17. (If you no longer have you're user manual for the Asus K8V-MX MB you can download it from Asus by clicking on this link):
http://support.asus.com/download/download.aspx?modelname=K8V-MX&SLanguage=en-us

Remove the SATA data cable & clean both ends of the cable with a few drops of alcohol on to a cotton swab. Than clean both SATA ports on the motherboard using the same method.
Also clean the SATA power connectors in the same fashion. (Allow time for the alcohol to dry).
You can help it dry using some canned air.
Re-connect the SATA data cable & SATA power cable to the SATA drive. (Check all other connections within the PC for good connections before closing case). (SATA data & power connectors are easily knocked loose, so be careful).
Plug the power cord back into the PC & boot the PC. Enter you're bios. Check the main menu & make sure the bios has listed the SATA drive. Than go to Boot menu. Page 2-27, 2-28 in the manual. Make sure you see the SATA drive listed here. If you are sure the SATA drive was listed in the main menu than it must also be listed in the Boot menu.
If it is not listed in the Boot menu than there is a problem with you're bios. You're board is warranted for three years from manufactures date. Please call Asus tech at 1-812-282-2787.
M-F 9:00AM to 5:00PM EST. You will need the serial number printed on a white label located on the pink LPT port. You can see this only from within the PC. Asus will ask for that S/N to determine if you're board is still within warranty. If it is, make sure you get a case number & instruction before ending the call.

Good Luck!
Mike