Windows 7 - One of my hard drives have disappeared from the system

Yesterday I installed a new SSD and re-installed my OS and a bunch of non-game programs onto it, then formatted my 500GB WD HDD which used to hold the OS and all programs and games, while leaving my remaining 250 WD HDD untouched as it had file backups and media on it.

All the controllers are running in AHCI mode in both the BIOS and Windows 7

Yesterday all the drives were running fine, plus I installed 2 games onto the 500GB HDD and I shut down and rebooted many times during update installs yesterday, with all drives showing up fine.

Today, however, the 500GB HDD does not show up in either the BIOS (using auto-detect) or on "My Computer" in Windows.

So I checked the cables - all seemed ok. I changed the SATA port from SATA_2 to SATA_4 but still no luck. I updated the motherboard BIOS from F6 to F8 - no change. I tried to change SATA ports 4&5 to IDE mode and run it in SATA_4 - no luck (reverted to AHCI). I checked to see if the platter was spinning by vibration - I feel vibration but I don't know if it's from the HDD or from the 250GB one below it as the 250GB drive is warm, whereas the 500GB one is not!

Motherboard: Gigabyte GA-MA790XT-UD4P (AM3) Revision 1.0 BIOS F8
Drive configuation:

SATA_0 (AHCI) LG 22x DVDRW
SATA_1 (AHCI) Corsair 60GB Force 3 SATA III SSD (Forceware 1.3.3)
SATA_2 (AHCI) Empty (used to hold Western Digital Caviar Blue 500GB SATA II 7,200rpm, 16MB Cache 3.5" HDD)
SATA_3 (AHCI) Empty (used to hold Western Digital Caviar Blue 250GB SATA II 7,200rpm, 16MB Cache 3.5" HDD)
SATA_4 (AHCI) Western Digital Caviar Blue 500GB SATA II 7,200rpm, 16MB Cache 3.5" HDD (***NOT BEING DETECTED***)
SATA_5 (AHCI) Western Digital Caviar Blue 250GB SATA II 7,200rpm, 16MB Cache 3.5" HDD

Again, it was working fine yesterday, however when I turned the system on today, it was not detected. I really hope the drive hasn't failed - those things cost a fortune now since the floods in and around Taiwan!

My 250GB drive went into idle and now (20 mins idle) there are no vibrations, so I guess that the 500GB drive wasn't spinning anyway

OK m8 check your bios and update or internal pci sata card to bypass any issue

Fixed it - a lose power connection which I thought was in there properly - I fell like such an idiot, oh well,merry Christmas (admins can delete this if they want because I can't find out how).

Congrats on finding the problem, these things happen.

Glad to hear it's resolved.