Thanks all, I have solved the problem by downloading and burning a fresh ISO but this time the version for AMD64 which is what my laptop is.
Then I formated the HD and done a new installation of winxp the used the new cd of ubuntu 8.1 AMD64. now all is working, I only have to re-install my software but now I'm goint to bed I have been at it 10 hours.
Many thanks good night
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