That can happen. As we say here: "You only lose what you didn't backup." That's why people having "important files" should know how to make backups.
Now all you can do is to try recovery programs. Start with free Recuva from Piriform. If no luck, try other programs or - to be on the safe side - go to a data recovery company.
When I go to My Computer, the total and free space of the drive isn't displayed. This all happened after I tried to allocate free space from my D: drive to my C: drive since the latter's memory was running out. I got an error saying that the allocation was cancelled because I was running a program, and then this happened. I can't access my drive anymore, and when I went to Disk Management it showed that my D: drive became a RAW file system.
I had tons of important files in there. Is there any way that I can recover them?

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