Proper naming of enum values for C#

enum AvailableSpace {
   Percent10,
   Percent20,
   SqF500,
   SqF600
}

public enum OperatingSystem
{
    Windows95,
    Windows98,
    Windows2000,
    WindowsXP,
    WindowsVista,
    MacOSClassic,
    MacOSXTiger,
    MacOSXLeopard
}