The problem between your C: and D: drives is a little hard to understand, are these physically separate drives or just partitions of the same drive.
For your ethernet card, try right-clicking on my computer and selecting manage
once there find device manager in the left window pane
Then look through the list to find network adapters, see if yours is on the list and right click it and select enable or update the driver, this might jump start it so that it can function again.
Then you should be able to work with it as before if you follow the prompts, this probably occurred because of the other issue that you were dealing with in updating your hard disk(s).
I hope that helps