Hello,
Your first major mistake was to upgrade your computer without making a backup. I bet you will learn from this, and not make this mistake a second time. Backups are the lifeblood of your data. Also, had your data been on a different partition, you could re-format C: and not caused a problem with your data on D: I realize this does not help you, but it may inspire you to take better care of your machine.
If this box was sent to me for repair, I would take the hard drive out, and put it into a second computer as a slave hard drive. Boot that one up, and then copy the data files off of it. Then, I would be in a position to re-partition the broken setup, reformat the drives, and setup the machine and then setup a backup strategy. If you try this, make sure you set the IDE jumpers accordingly for primary and slave.
If you have a network available, you might try booting Knoppix or a different linux that is all contained on a CD-ROM. You can then see if it will access the NTFS volume, and then let you copy the data to a server.
In the end though, I think you are going to end up starting over from scratch with the FORMAT utility, and rebuilding from square one. It is my personal expierience that trying voodoo repairs and other tricks with the registry and that are …