plain text opens instead of formatted spreadsheet
 

Below you see what happens when I open a excel file. The file is good as I
can open on other computers correctly. I am using office 2000 on an xp
computer.
Any ideas how to fix this?

<?xml version="1.0"?
<ss:Workbook xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet"
<ss:Styles
<ss:Style ss:ID="wheader9725t332w0f"<ss:Alignment ss:Horizontal="Left"
ss:Vertical="Bottom"/<ss:Font ss:Family="Swiss"