I turned off my computer by pressing a turn off button for a long time. Then I turned it on. Usually it doesn't ask for password, but this time it did.So I tried to enter my password and it seemingly worked - I'm seeing a usual black window with some white text on it for a second, but then it returns to asking password again.It knows the password is right, because if I enter the wrong password it tells me it's wrong immediately.How should I go about solving this problem? I'm very afraid of losing my data.Some details that may be relevant:  now it's very noisy.  Linux username 3.13.0-43-generic #72-Ubuntu SMP Mon Dec 8 19:35:06 UTC  2014 x86_64 x86_64 x86_64 GNU/Linux  I am running it in guest session.
When I boot Linux, it asks for password, pretends to proceed, but then returns to asking it again
linux;password;crash