I have dual boot and I keep all my data in separate partition and now I am not able to open that partition in freya.
If you are using Windows 8:
Change what the power buttons do
This should avoid any problems in the future with unmountable partitions. For safety, shutdown your windows with your
Ctrl key pressed, it forces a regular shutdown.
If that doesn't fix the issue, that's when you should follow Dusan's indications.
if you don't change this setting in your Windows you might run into this issue everytime you boot into elementary OS coming from Windows.
Source and pics: Dual Mount issues
One of the many accounts I've seen of corruptions happening after ntfsfix: Don’t use ntfsfix in Linux, just turn off Fast Boot in Windows