>I created a russian chm file in russian windows and specified
>a russian language everywhere.
>I usede HTML help workshop shipped with VFP 7.
>
>If I open this CHM file in US Windows (russian fonts are installed)
>its contents is totally unreadable: russian characters are not shown in contents pane. It seems that chm viewer selects some other font.

Try to add to HTML header:

<meta http-equiv="Content-Type" content="text/html; charset=windows-1251">
<meta http-equiv="Content-Language" content="ru">