After that I install a 2006AutoCAD the TANK input toolbar buttons became off.

AutoCad and TANK should not conflict or otherwise step on each other. In TANK, use the "View" menu to turn the toolbars back on.

The input toolbar exist and I mean that the buttons of the input & analysis are freezed (also in input menu).

The buttons and menu are disabled by the software when one of the component modules (such as output) is started. Look in your task bar and see how many "TANK icons" you have. If there is more than one, right click the 2nd one and select maximize.

Does this resolve the issue?

no! I think this problem is related to the REGISTRY of XP.

Well, if AutoCAD fouled up the TANK registry entries, then uninstall TANK, then reinstall TANK.

(I still find it hard to believe this is what happened.)

It didn't changed.

E-mail a screen capture to techsupport@coade.com.