Help:Problem with calculation

In my version of Excel 2002 when I try calculate for example 10.5/2 it does not work. But if put a "," instead of "." like 10,5/2 it works fine. It looks like it only recognizes a coma. Is there any solution to this problem? All data I have has "." insted of "," so I can't really change it manually because there is too much of it. Any help would be appreciated, thanks.

I use 2003
see if you are able to go to tools options international
see if there is a checkbox called use system seperators
or something like that,
the , is used in some countries