Iam using HP Pavilion dv6226TX and now I am facing a problem sometimes when I s  

Iam using HP Pavilion dv6226TX and now I am facing a problem sometimes when I start the notebook.
While booting it displays the HP logo splash screen ,the Microsoft Windows logo splash screen and then a blank screen. The windows login screen is never displayed.
I press and hold the power button to switch off the notebook and start again after few minutes,
I used to select "Start windows normally" option and after that again the same problem is seen.
The windows login screen some times appears and sometimes not.
so please provide solution for my problem.