I dont' know what I did, exactly, but it works now!
I took your advice and opened the case to clean out the dust and check the data and power connections.
Then I turned on the power to see if the 250GB drive was even getting power.
I took out the Live CD just to see where it would go, and it started booting up. (my first thought was, "How is that possible?) I entered safe mode, (just in case), and ran testdisk (just in case). It saw the 250GB Drive! and the test results were ok, so I rebooted and it went right to my desktop! YAY! What a welcome sight.
I shut down gracefully and rebooted again just to make sure. (I'm only a little neurotic.)
Thank you for all your advise.