Excel 2003 (Win 7) Multiple Programs

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Hi All

I have recently upgraded to Windows 7, but would like to keep using Excel 2003.

Unfortuantely, whenever I open a spreadsheet, Excel opens a program each time. So, instead of having one excel with 3 files, I have 3 files and 3 excel programmes running.
This means that I cannot copy sheets to and from each other, and some formulas don't work. Also, when I customise the shortcuts, everytime I reopen I lose my customisation.

Any help on this would be much appreciated.

Thanks

Splash.