Windows ANSI (codepage 1252) is likely to be the default setting on many Windows systems.
The only difference between CP1252 and ISO-8859-1 is that the former uses the range 0x80-0x9f to represent a set of additional glyphs (e.g. Euro, 'curly' quotes, per-mille symbol) which ISO-8859-1 specifies as 'undefined control codes'.
See the Wiki entries for these two coded-character-sets.
This sort of compatibility issue is one reason why UTF-8 (a multi-byte encoding) is becoming more-and-more popular.
But (obviously) if your target application does not support UTF-8, this is not an option.
