I got a phone call yesterday from my user about Windows XP not activated. This problem is a first in my years with Windows XP. All the XP machines are installed using a volume license or pre-installed by the vendor. No activation is ever required.
My first step was just following the on-screen wizard to activate it again. It appeared to be activated, then a message came up.
“A problem is preventing Windows from accurately checking the license for this computer”
There is an error code at the end. Microsoft has an article about this particular error and here is the link.
There are quite a few workarounds that you can try. What worked for my is not mentioned in the article. I did a repair installation and that fixed it.