Sorry if I'm a bit thick but I'm not sure what help you want.
If you have upgraded from XP to Vista it is likely you have lost it.
If you have tried the Dell method (I believe F10) and nothing happens that confirms that it has probably gone.
I am not sure what you mean about not wanting to take a chance.
Should I upgrade to Windows 10? 8 reasons why you should upgrade to Windows 10... and 2 why you…