error opening excel 2003 spreadsheet

Hi,
Everytime i try to open an excel spreadsheet (say test.xls) it will automatically create a duplicate of it (test1.xls) and put a “1” with the original file name and opens the duplicate one. To open the original (test.xls) i have to close down the duplicate one and open it again from File-Open in Menu Toolbars.
Any help to get rid of the problem will be really appreciated.