A long time ago i tried partitioning, somehow accidently deleted my entire old computer's drive, and now i can't access 500 gigs of my hard drive.

http://i.imgur.com/1A6iH6v.png

When i got my new computer, my dad's coworker split the hard drive into two, leaving 500 gigs on another drive, and he put the files from my old computer on there. That only used up 85/488 gigs on that new drive. Later on, i decided that i wanted to take the free space from that drive and switch it to my C: drive. Yahoo answers said a third party program would let me do that, so i downloaded Partition Magic i believe it was called, it didnt seem to work so i just deleted it off the computer. I really have no idea what happened, but all of a sudden the drive with my old computer was gone, so was the extra space and such.
I have no clue what happened, i never even used the program to touch any form of partition. Anyway, that was like a year or two ago.

That picture shows my disks now, but i have no clue how to use that free space thats just chilling there, because im running low on space on my C: Drive. Any ideas? Ill answer questions the best that i can but like i said, that was a couple years ago and i litterally have no idea why it happened. Thanks.