Before 2010, Excel was a prisoner. It was locked inside a 32-bit memory address space, meaning it could only utilize (or 4 GB with tricks). For a financial modeler trying to process 1.5 million rows of data, Excel would hit the "Out of Memory" error faster than you could press Ctrl+S.
*Looking for MS Office 2010 Excel X64 -thethingy- (The old Data Analysis pack?) * MICROSOFT OFFICE 2010 EXCEL X64 -thethingy-