No , its not an orginal CD. It is a .nrg image that I downloaded from a torrent site. Anyway I deleted it. But I found a very old XP Pro CD SP1 that I had. I stopped using that CD because it only had SP1 and whenever I tried going online to do a Windows Update, within 5 mins I would get viruses since it didnt have security patches. But I just used this CD to SlipStream SP3. Fortunately it worked and it even gave me no errors while setup was copying the files after formatting. But the problem is that it gives me an invalid Product Key error. I have the right key. I have used it many times. I wonder why is it giving me problem. I explored the CD and went to the "i386" folder. I opened UNATTENDED.TXT file. I used that Key also. It still gave me an Invalid Key error. What could be the issue ?