Maybe the account you have put in is not the right one. If you can't remember the old account you can try with the command prompt method to reset the password. Here is how to:
Step 1: Start your win 7 computer and press “F8″ while the computer boots up. Scroll down to “Safe Mode with Command Prompt” with the arrow keys on the keyboard and press “Enter.” Your computer starts in Safe Mode with Command Prompt.
Step 2: Select the Administrator account that appears on the screen, then enter command prompt. Type: net user ****** 123456 and enter (****** is the account name and 123456 is the new password), it will show you a message that "the command complete successfully".
Step 3: Restart your win 7 computer, then you can log in as ****** with the password 123456. You can go to "Control Panel" to change your account password if necessary.
If this way doesn't work you can resort to Windows Password Recovery Tool Ultimate to reset it.