Symbol or character
Specifies the punctuation used to separate the fractional part of a decimal number from the whole-number part.
To change the value of this entry, double-click Regional Options in Control Panel. Click the Currency tab, and then click the Decimal symbol list.
Regional Options in Control Panel restricts this entry from accepting the numeric digits 0–9. Editing the registry directly to set this value to a numeric digit could have one of two effects:
If an application calls the GetNumberFormat API, the system will use the default symbol for the locale.
If an application does not use the GetNumberFormat API and the application does not check the format itself, the numeric value will be used. This could cause errors if the value is used in calculations.