Does Office 2007 work on Windows XP? Yes, it does.
Yes, Office 2007 is fully supported when used with Windows XP. This question is one I'd heard a few times in the past week; there is a lingering perception that Vista is required to use the 2007 versions of the products. Rest assured, this is not the case.
System requirements are posted here: http://office.microsoft.com/en-us/products/HA101668651033.aspx