|There are two connectors to your hard drive, one is your signal/data cable and the other is your power connector from your power supply. If you have a spare unused one of these, switch it out with the spare.|
If a drive does not show up in My Computer, look in Disk Manager to see if it shows up there, if it does and does not have a drive letter, try assigning one. If that does not work you may need to repartition and format the drive, BUT YOU WILL LOOSE ANY DATA ON THE DRIVE if you do this.
How does it show up in BIOS and does (and how) it shows up in Disk Manager?
You have to be a little bit crazy to keep you from going insane.