You can manually start in-camera sensor cleaning on your Canon via Sensor Cleaning>Clean Now in the menu. But if dust spots remain you’ll need to clean it with swabs, see Step 4 below.
The Canon EOS 400D, called Digital Rebel XTi ... an integrated image sensor vibrating cleaning system, the precise 9-point auto focus system from the EOS 30D, improved grip, and a bigger 2.5 ...