As this issue, here are some possible issue to fix your trouble.
- CAPS LOCK might be on.
Passwords in Windows are case-sensitive, which means that every time you type your password, you have to capitalize each letter in exactly the same way that you did when you first created it. If you have accidentally pressed CAPS LOCK, then you're inadvertently typing your password in all capital letters. Make sure CAPS LOCK is off, and then type your password again.
- An administrator on the computer might have reset your password.
If your computer is on a network, a network administrator has the ability to reset your password. If you think this might be the problem, check with your network administrator. If your computer is in a workgroup, anyone who has an administrator account on the computer can change your Windows password.
- You might be trying to log on to the wrong user account
If you have more than one user account on the computer, make sure you're logging on to the account that matches the password you're using.
- You might be typing the wrong password.
If you can't remember your password, you need to reset Windows password, either with a Windows password reset disk or an administrator account. As this touble, it seems to be a little annoying. Of course, you still can reset the forgotten Windows password with a third party software. Windows Password Unlocker is taken as one of the most efficient and powerful Windows password recovery tool, which can reset the user and admin password with a bootable CD/DVD/USB in minutes.