Hard Drive is full for no obvious reasons

Hi! I bought a new Sony Vaio laptop with Windows 8 pre-installed couple months ago; and all I have done since was installing just the MS Office and the Antivirus softwares. Now for no apparent reasons it shows the hard drive is full and I can not do anything with it. I've tried to create a system recovery with an USB flash drive, but it won't let me do it either. Please help & thanks.

System Specs would save a lot of time

Download and run Treesize Free. Get the zip file version and download to a flash drive then unzip it there so you don't use up any more disk space. Run it and you'll see where all the drive space has gone.