I installed Windows 7 and now I want to uninstall it, so go back to my Windows Vista.
Understanding downgrade OEM rights
How to restore a Windows 7-based computer to a previous Windows installation by using the Windows.old folder:
how to uninstall Windows 7:
How To Downgrade From Windows 7 To Vista (Step-by-Step Guide)
if you dont have the windows.old folder then you have to format and reinstal windows vista, so first boot on windows vista and choose format then clean instal.