I think mf007's link will only download the Service Pack.
Do you have a friend who has a proper Microsoft Vista Home Basic CD? If so, it's perfectly legal for you to use it to reinstall the OS on your computer. Just make sure that you use your own product key from the sticker on your computer.
Alternatively, are you sure that the computer manufacturer didn't include a Windows restore sector on your hard drive?
This thread is now locked and can not be replied to.