Reset the CMOS with the jumper on the motherboard. Or, if you can't find it/don't want to do that then just pull the battery again, unplug from the wall, and press the power button (perhaps a couple times for good measure). Then put the battery back in and plug it in and start up.
Also go through and see that everything is set properly in the BIOS so it does see the drives (example - turn off RAID if you aren't using the drives in RAID).
My post seems redundant in part, because the dude double posted and I replied to the 'other' one before seeing the one with replies. I've merged the threads now.