There is no serial number for Office. The Product ID, which is necessary to
obtain product support, can be found by opening an Office X application,
going to <Application> -> About <application>, and looking under your name
and organization.
If you're referring to a lost CD key, you can request a new one from
Microsoft Product Support Services. You'll need proof of ownership to get
one.
<
http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS>
Remember that you can only have Office installed on one desktop and one
laptop. If you're new computer is another desktop, another laptop, or a
third computer, you need to uninstall Office from one of the other machines.
