None of my harddrives work since I added another one. One doesnt even show up in the bios anymore. Everything just boots to a black screen with a flashing cursor. Not even Windows vista dvd or Windows 7 dvd will boot.
I know this might sound crazy but it is possible your psu is going. I installed a second hd in a customers pc and as soon as I plugged the new drive in the computer would not boot but after unplugging the new drive it worked fine. I ended up replacing the psu and everything worked fine. Good luck.