i got a call from Lenovo, and they told me the the bios is not calling for the ac adapter, it´s because of the not original battery. The bios recognizes that it´s not an original battery so it shows this error with the power. He knows this problem.
But he said to me it´s not easy, it´s allready nearly impossible to get a battery for the T600 with minimum 70% capacity left, so the bios will do the update. He said if you buy an original battery on ebay this thing is nearly 10 years old, it can´t have 70% capacity left it´s dead.
He also said if the system is running well with XP i don´t have to do the update, because the changes were so little.
The best thing is i sent the e-mail to IBM yesterday and they sent me an e-mail today that i have to mail at lenovo, so I did today and half an hour later i got the call back ! This is service THANK YOU Lenovo