We can't change the behavior of MS Word 2000/XP as this program also uses this key combination. We have created a macro for this.
Select any word in MS Word 2000/XP and click the 'Look Up In Pop Up Dictionary' button on the Pop-Up Dictionary toolbar in MS Word 2000/XP:
If you do not see this toolbar right-click any toolbar in MS Word 2000/XP and in the appeared menu tick off the Pop-Up Dictionary toolbar.
If you can't find this toolbar in the menu you have not installed the macro. Uninstall Pop-Up Dictionary and install it again. Install to Microsoft Word option should be ticked off (it is by default). Note that this macro is available only in Pop-Up Dictionary 4.2 build 295 or higher.