77,1 * 850 = ???
You probably already heard about the bug in Microsoft Excel 2007.
Former Excel-Teammember and Software-Development guru Joel Spolsky has a very nice writeup on the reasons, background, etc.
Personally, I think this „bug” is Microsofts devilish plot to move Excel to 64-bit-platforms-only „to support the higher precision mathematical operations your customers require”. ;)