I believe Belka asks a simple thing at first, proper display of English and Russian, regardless of language choosen by the user. The answer is simple, convert to UTF-8 and add corresponding Russian files, deleting the ANSI codepage ones.
There is one more solution, with a little cheat, Multilingual in SMF 1.1RC2 without UTF for Greek and other languages?
, works well for Greek, might as well work for Russian, no patch needed. However UTF-8 is the formal approach.
Adding a CMS like TinyPortal
will let you have multilingual menus, blocks and other language specific choices, other SMF specific portals
may have similar choices to some extent but I have no experience with them. The choice is yours.