The short answer is no. If a volumn licensing product is purchased, then you can install it on as many computers as you bought licensing for. You can re-install it on the same machine as many times as you want. MS Office allows you to install it on one PC and your laptop for your sole use. To verify your specific product read the EULA that shipped with it.

If you have a retail version, you are allowed to unistall it from the first system, then install it to another. If you have an OEM version it can only ever be used on the original system it was installed to.

A volume license is required for installation on more than one PC at the same time, as mentioned above.

Well , I just reformatted over the weekend. I was lanning over at a friends house, and he was helping me reformat. I forgot my XP Home cd key, so he let me use his. It worked fine. And when I went to activate it, it also worked. So from my experience, it sound's like you can.

I think another person there said you can use the same key on up to 3 computers.

That is incorrect information, RyanBoggs001.

I would strongly suspect that following the advice of those friends would get you into trouble sooner or later

You will find out the correct information about Windows XP product activation by reading this document and its related links.

Thanks Catweazle for the link; I searched and searched and couldn't find this information. Here's a quote from MS verifying that what you and Bentkey said are, in fact, correct (in case anyone else is wondering):

"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.)"