Depends on the kind of XP (pre-installed or not) and (if retail) if you registered it. If you're a Technet member, you could still download XP. I don't know of any other download sources.
You might be able to order a replacement CD with the manufacturer. Or you might be able to use another XP CD (friend, family, etc) for such a basic repair only. You don't know until you tried.
I lost my windows xp sp3 profesional cd and now I need it to repair my pc (NTLDR is missing error), It is possible to get a new xp sp3 (donwload on another computer and then install it on the malfunction PC ) ?
I've heard that because my windows xp was the originall cd I can get a new copy using my motherboard info ,get the software (new xp sp3), and then make a new cd ; it is this possible???