** [White Westinghouse dryer] model number DE400KDW-2 When I run the dryer it works fine, but I get this annoying squeaking noise. **
Common areas for squeaking/squealing sounds on dryers are a worn idler (belt tension) pulley, worn drum rollers (not used on your model), worn front drum slides and the rear drum shaft and bearing.
On your particular model dryer, the rear drum bearing and shaft are the worst for creating a metallic screeching noise once the drum shaft has worn through the shaft bearing. The drum shaft and bearing for your model come together in a service kit (see the following link).
BTW. If required, do NOT put off that particular repair for long as the drum shaft can get cut right in half. That will allow the drum to drop which can cause more extensive (and expensive to repair) damage! A stitch in time...