I have an old HP personal computer that recently crashed. I have replaced the HD. Then I used a windows XP home cd from another machine. I was able to install Windows but it will not accept my product key. I assume this is happening because the key doesn't match the CD. The problem is that I have long lost the original installation CD. So I have a valid license for XP home but I don't know how I can use it. I refuse to buy another copy of Windows. And HP says my PC is 5 yrs old and cannot send me a new CD. What can I do?