I have the WINDOWS XP CD and it was in a sealed pack but when I opened it there was a message that says "THE CERTIFICATE OF AUTHENTICITY LABEL HAS BEEN REMOVED BY YOUR PC MANUFACTURER AND ATTACHED TO YOU PC".
Well, I have got a new case for my computer since then and I don't see that label anywhere.
Does that mean I can't use it????
Sorry to say, but it all depends...
Here's the deal.
If the installation program asks for the product key (which is usually printed on the certificate of authenticity) you'll be out of luck and not able to install unless you have it written down somewhere - or there's a separate card, or a sticker inside the CD case that has a copy of that information.
However, if the CD has been setup by the manufacturer as a "Restoration Disk" (which usually says something like "product recovery CD" and does not look like a an over-the counter Microsoft product) then there's a very good chance you won't need to enter a product key - nor will you need to "activate" once it's been installed. Microsoft did allow certain manufacturers to "preauthorize and pre-activate" their product recovery disks. So if you have one of these, all you'll probably need to do is boot from it and tell it to reinstall WIndows.
Unfortunately, if you have replaced a bunch of hardware, you'll still need to get the appropriate drivers for anything that didn't come with your machine. Neither a generic Windows CD nor the recovery CD will have working drivers for everything you've since installed on your machine. Expect to do some web browsing to download everything you'll need.
One other thing, which I'll bring to your attention since I've run into this issue in the past. If you had your motherboard
replaced by anyone other than the original manufacturer, you can forget about using their OEM recovery CD. Those CDs are almost always keyed to look for the original manufacturer's mobos, and will not work if they can't find one.
Case 1: You have an old Dell and you replaced everything except
the original motherboard. (The Dell recovery disk should
Case 2: You have an old Dell and you replaced nothing but
the Dell motherboard with a board from a different manufacturer. (The Dell recovery disk will not
Also bear in mind that once you get your copy of Windows reinstalled, you'll still need to download and install all the updates and service packs which have been released since your CD was mastered. Windows Update Service will handle that part for you, but the total download size (especially if it includes service packs) will be huge. So you'll need at least a DSL or cable connection to the Internet for it to be practical. Don't even try it on 56K dial-up unless you can afford to give it a few days to get all the downloads.
Hope this helped.