This PC is the new name for My Computer in Win 8.1, it probably was in Win 8 but I didn't pay that much attention to it.
If you double click on This PC can you see your C: Drive and if you double click on that can you see all the files such as Program Files and Windows etc?
Are all your User files also on C: or do you have the data on a different partition or hard drive?
If you can see all your documents, music, pictures, videos it may be simplest just to save all those to an external hard drive, or big USB memory stick, then re-install Windows 8 plus your programmes.
Or maybe you can get into Safe Mode and do a System Restore from that, or Last Good Configuration.