well i guess here is your answer,

How does Microsoft Product Activation work?Product Activation works by validating that the software's product key, required as part of product installation, has not been used on more PCs than is allowed by the software's end user license agreement (EULA). In general, Windows XP can be installed on one PC and Office 2003 or Office XP can be installed on one PC and the laptop computer used by the user of the one PC. (For specifics, please see the EULA accompanying your product.) Product key information, in the form of the product ID, is sent along with a "hardware hash" (a non-unique number generated from the PC's hardware configuration) to Microsoft's activation system during activation. In Windows XP SP1, the product key itself is sent in addition to the product ID. Activation is completed either directly via the Internet or by a telephone call to a customer service representative. Activations on the same PC using the same product key are unlimited. Product Activation discourages piracy by limiting the number of times a product key can be activated on different PCs.



So i guess its office xp you can use on 2 pc's

there is a ton of info on google hehe

thanks biker666_05