What medium (CD) did you use to install XP? I have a few tools to make you genuine, if you used a patched CD, methinks.
Try this. Copy to batch file then run as administrator:
Code:
attrib -s -h -r %systemroot%\system32\drivers\etc\hosts
echo 127.0.0.1 mpa.one.microsoft.com >> %systemroot%\system32\drivers\etc\hosts
Basically, the hosts file mentioned in the code is where you can reroute addresses. For instance, if you added 127.0.0.1 www.google.com, you would not be able to access www.google.com because the hosts file is saying that google.com's IP address is 127.0.0.1 (which turns out to be your own computer!). In such this case, if you aren't running a web server, you'll get an error.
Such being said, Microsoft left an open door, it seems, in case the activation servers are down. With this code, you are tricking XP into thinking that the servers are down.
Run that, and then visit microsoft.com/genuine and click validate windows. If you check in as genuine, good! If not, call back.