"Your activation period has expired" Error

You may faced an issue "Your activation period has expired" in Windows Vista. You may receive the following error message when you start Windows Vista:--
Symptoms:--
When we try to start a Windows Vista based computer then we can get the following error messages:--
# Activate Windows Now
# Your activation period has expired and Windows is no longer working.
# To use Windows you must activate this copy of Windows.

Cause:--
This issue may occur for one or more of the following reasons:--
# You did not activate Windows Vista within the 30-day activation period.
# Windows Vista detects that the hardware on your computer has changed significantly and that you did not reactivate Windows Vista within the 3-day grace period for re-activation.
# You are running a version of Windows Vista that was detected as non-genuine. For more information, see the "Resolution" section.

If you have a Windows Genuine Advantage copy of Windows Vista then you can get rid off this issue by these methods:--
Troubleshooting Methods:--
We can get rid off this issue by following these troubleshtooing methods:--
Method 1: Enter your product key
1. Click Retype your product key in the Activate Windows Now pop-up message.
2. Accept the User acceptance prompt.
3. Type the product key, and then click Next.

Method 2: Activate Windows Vista by using the automated telephone system
To activate Windows Vista by telephone, you must use an automated telephone system. To activate Windows Vista by using the automated telephone system, follow these steps:
1. Click Start, and then click Computer.
2. On the toolbar, click System properties, and then click Click here to activate Windows now in the Windows activation section. If you are prompted for an administrator password or for a confirmation, type the password, or click Continue.
3. Click Show me other ways to Activate.
4. Click Use the automated phone system, and then follow the instructions.

Method 3: Use the Windows Management Instrumentation command-line (WMIC) utility to view the product identification number
1. In the address bar of Internet Explorer 7, type %windir%\explorer.exe, and then press ENTER to open Windows Explorer and the taskbar.
2. At a command prompt that has elevated user rights, type wmic, and then press ENTER.

Method 4: Contact Microsoft
If Windows detects that the hardware on your computer has changed significantly, and the previous method does not solve your problem, you may have to contact Microsoft for help. To view the Microsoft Activation Centers Worldwide Telephone Numbers list, visit the following Microsoft Web site:
http://go.microsoft.com/fwlink/?LinkId=71142 (http://go.microsoft.com/fwlink/?LinkId=71142)