How about:
for (unsigned i = n ; i-- > 0 ; ){ // do stuff with i}
for ( unsigned int loopIndex = n; loopIndex > 0; --loopIndex ) { unsigned int i = loopIndex - 1; ...}
or
for ( unsigned int loopIndex = 0; loopIndex < n; ++loopIndex ) { unsigned int i = n - loopIndex - 1; ...}
for ( unsigned int i = n; i != 0; i-- ) { // do something with i - 1 ... }
Note that if you use C++ as well as C, using != is a good habit to get into for when you switch to using iterators, where <= etc. may not be available.