Because you can see the partition using Quick Search and list your files, I believe you have a very good chance of writing a new partition table and seeing your drive again but because the files are so important to your, I believe it is best to copy over the most important files first.
In order to copy the files and or folders from the 1TB drive to the 500GB drive you will have to download the Windows version of Testdisk. When attaching the external drives, make a note of the drive letters assigned to each.
After downloading Testdisk and unzipping the folder in an admin accout, run it and do the same steps, using quick search and then pressing "P" to list the files. You will notice at the left a series of letters. Anything that starts with a "d" is a directory (folder) with files contained within.
In order to select multiple files and or directories highlight the file or directory you wish and press the ":" key (bleep + ;). Do not select "a" as you do not want to copy over all files. The selected folder or file will turn green. After your selection is done press "C", not lower case "c". It will show a window that defaults to the location of your unzipped Testdisk folder which you do not want.
Press the left arrow key twice. You should now see a listing of your drives. At the far right is the assigned letter to the drive. Highlight the letter that corresponds to your 500GB drive and press the right arrow key. You should see "Directory X:" at the top where "X" is the drive letter of your 500GB drive. Now press "C", not lower case "c" and the file will be copied and you will go back to the file listing again for more selections. You should now see that file on your 500GB drive in "Computer". I would start off by copying one file that is not that important and see how it goes. If it goes okay, then start selecting your most important files.
If you aren't sure, post back with any questions and I will try to explain in more detail if I can.
Screenshot of File lising showing selection option at bottom of window
And I forgot. to BC.
Edited by JohnC_21, 14 June 2014 - 10:28 AM.