I create an excel file corrupt in win7

I have a problem exporting a grid to excel.
Windows7 64bit Office 2010 creates the excel file, but is not valid.
Windows XP Office 2003 creates good excel file.
The php code is identical in the 2 cases, and the data are the same.
The file created in windows7 is not read by Office 2003.
The error message “The file is corrupt and can not be opened”

Can you provide the example of such broken excel file

File corrupt
http://93.63.134.103/xdhtmlx/grid_corrupt.xls
File ok
http://93.63.134.103/xdhtmlx/grid_ok.xls

win7 64bit , Apache 2.2 , php 5.3