Stuck with Windows Vista activation error 0xC004F033

Hi,
I utilize Windows Vista in my PC. Previously I was running Windows XP on my computer but somehow it worn-out. So, I purchased a new copy of Windows vista from Microsoft website. But each time I try to activate Windows Vista; I am just getting the following error message:
Error code |
Description |
0xC004F033 |
The Software Licensing Service reported that the product key is not allowed to be installed. Please see the event log for details. |
I just stuck in one place. Can anyone help me!
