Question : Windows XP Validate after 30 days expiry

I am working on a client's XP computer which has not been validated and as such (i suspect)  IE's functionality has been disabled. I can't access the web although IE although the machine will download updates.I suspect the client had some problem, tried to repair the OS but then failed to validate within the 30 days time limit. The box has a Windows genuine key on it.  
I am trying to get around either re repairing XP from the install disk and or having to call MS.
My questions:
1) How do I replace the current key in the machine with the one listed on the box? I understand
magical jelly bean keyfinder has this capability. If it does what are the exact procedures I need to follow? I know I can disable Windows validation but I understand it will just come back with future updates.

2) After I replace the key how do I access the web (Firefox??) to validate.
Thanks

Answer : Windows XP Validate after 30 days expiry

You can use the Microsoft Key Updater Tool to update the key and it will validate it for you.

http://www.winmatrix.com/forums/index.php?/topic/9539-microsoft-windows-product-key-update-tool/