Thanks Boogieman for your response. I do not have any partition, just C drive. So everything is in it. By everything I mean windows, some games, videos, songs, pictures, documents, some softwares, etc. Hard drive is 500 GB. I do not have any software for cleaning any files or folders. I have avast as my antivirus. After I found the sudden increase in space, I ran malwarebyte and superantispyware. Both did not find anything. However, I have not manually acanned with avast yet. As of now I do not notice any missing files. All the programs that I tried running are running fine. So I am a little freaked out why this happened.
Thanks.