Have a dell latitude i bought that has xp professional installed on it.It came with vista installed on it originally. I have the restore disk and the code numbers too. It worked fine for two days, now it shows error on disk on start up. I have to start windows on the startup. Then it works ok. I called the man i bought it from and said i needed to restore windows with the disk. Don't i need to erase the windows that is installed to use the restore disk? New to all of this. But i will learn. Thanks.