Is this lockscreen coming on due to the PC timing out after it's being left alone, or going to sleep? If so, go to:
Control Panel --> All Control Panel Items --> Power Options --> Change Plan Settings --> Change Advanced Power Settings, then under "Require a password on wakeup, set it to "No"
This page goes into more detail, such as how to turn off all password lock screens:
http://windows.microsoft.com/en-us/windows/change-password-requirement-computer-wakes#1TC=windows-7