There is no Solver in any version of Office 2008. It was a VBA add-in and
is no longer available because of the lack of VBA support in Office 2008.
If you want to see this functionality back in another form, be sure to send
the feature request to Microsoft. Click on this direct link to enter Mac
Product Feedback:
<http://www.microsoft.com/mac/default.aspx?pid=feedback>