BuddyPress.org

Older version of IE? which specifically? IE6? If so I’m afraid you’ll be out of luck or at least search long and hard to find themes that work with IE6 they should! but most won’t have taken this older browser into account bp-default hasn’t – by the look of things – done any or much testing in IE6.

There may be a few of the better ‘Premium’ themes around that have done their duty by browsers, but be prepared that if you really want layouts working in IE6 you might have to get someone to do that for you specifically.