Answer
For most European operating systems the default setting for the decimal place delimiter is a comma. For example: 12.34 is 12,34. ArcGIS recognizes and honors this configuration throughout ArcCatalog, ArcMap, and ArcToolbox with the following exceptions:
A. The SQL query language does not support decimal delimiters other than the period. When making a SQL query in ArcMap and ArcCatalog, use a period as the decimal delimiter regardless of the regional setting.
B. The Find and Replace tool does not find or replace numbers using the comma as the decimal delimiter.
C. Some of the property pages in ArcMap display numbers using the decimal delimiter even though the regional setting is set to use a comma.
ArcInfo Workstation does not support a decimal delimiter symbol other than the period.