In case that you want to change your Windows Vista key you do not have to reinstall Windows Vista but can use the command prompt to change it internally. You will have to activate the new key of course which can also be done by using the command prompt. To change your Windows Vista key do the following:

• Open the command prompt as an Administrator. You can do this by searching for command prompt and right-clicking the shortcut and selecting run as administrator from the menu
• Type “slmgr.vbs -ipk” followed by the new product key
• Type “slmgr.vbs -ato” to activate the new key