Every time Windows 7 is started it asks you to select the username and enter the password to access your system, there is no doubt that it is a very important security measure, but what if you are the only user of your system? In windows 7, you can easily get rid of the login prompt window, go through the following steps to achieve it.
Go to Start and type netplwiz in the Start Search and hit Enter. The User Accounts dialogue box will be displayed as shown in following screenshot.
Now uncheck Users must a enter username and password to use this computer option and press OK. Thats all, now reboot your system and you will never see the login window any more. If you are looking to disable the login window in Ubuntu, you can find it here. Enjoy!