Installing MS-Office without typing the product key repeatedly

Hello to all here. I need help on installing MS Excel. I want to setup MS Office XP without having to type the product key again and again. Let me clear the need. I have Office XP software. It seems boring to me to put the product key in every setup. Is there any trick to setup office without the product key? Please share it to help me. It will be great help for me as well as for others also.
