yeeahhh! i have had that too!! 2 or 3 times before! I was soooo mad I said all rude words to the stupid computer lol I can laugh about it now and i also got mad at all family members who're also using the computer I thought someone did it too me! but now i know why, for me the profile didnt work anymore because i was so stupid downloading something that pops up when you're on the internet...
BUT your files arent gone.. its only the profile who's lost.. all your files are still on the C
or where ever you put them. I first thought they where gone, but i found out i still had them/. So just make a new profile and copy- paste the files to the new one and delet the 'crashed' one!