<?php
/**
  * Generic preprocess that is still working on D7
  */
function MYTHEME_preprocess_views_view_fields(&$vars) {
  if (isset($vars['view']->name)) {
    $function = 'MYTHEME_preprocess_views_view_fields__' . $vars['view']->name . '__' . $vars['view']->current_display;

    if (function_exists($function)) {
     $function($vars);
    }
  }
}

/**
  * Then the specific preprocess that worked without the above code for D6
  */
function MYTHEME_preprocess_views_view_fields__VIEWNAME__DISPLAY(&$vars) {
  // my specific preprocess code
}
?>