Files Disappears !!! :(

hi ,
I face a big problem I bought my new pc only 3 weeks ago with very high specification and windows 7 ultimate 64bit after that I downloaded my pictures and videos on the pc suddenly all files and programs disappear and the pc become like the first time when I install the windows .
the size of the hard disk remain same shows that the files available but not visible I installed the windows on the other partition trying to get the files but same problem so please help me to get my files back.

Hi.

Sounds like you have a dual boot scenario without a dual boot option screen at startup or something along those lines.

Use disk management to see if all your partitions are assigned drive letters. If not, assign them and have a look then in Windows Explorer.