Office Button->Excel Options->Add-Ins->Manage Excel Add-Ins->select the following
Analysis ToolPak, Analysis ToolPak VBA, and Solver
If you have Office 2003, here is the converter.
It will allow you to open files that were made in Office 2007 and save them in Office 2003. Then you can work in Office 2003.
If you have a Mac, you will need to download StatPlus and use the following instructions:
