30 day warning notice

I habe bought a computer with it's own Optima installation cd, but when i
installed it, it gives a 30 day warning notice. It seems that this cd has
been used x amount of times and now I have to call Microsoft requesting a
new installation id. In what part of the registry can i find the section
that will over come this problem, but keep my cd able to be made a proper
copy of Windows xp home edition. When i used microsoft updates and such, it
tried to validate my copy and came back with unable to validate your
windows.

How can i over come this problem with out contacting Microsoft ???

Thank you
Peter
Australia