petra,
there are several things you can do to fix this image. your clone brush will help with the dust and scratches. just keep going there. cropping, like creeduk suggests would be good too. also, the salt and pepper filter in the noise tools would help. just be a bit careful there as you can blur an image pretty good with that, so use it sparingly. and after using it, try a sharpening.
for the black area on the right and the deep shadowing on the guy's face, a mix of tools might help here. you might want to mask some of the areas you dont want to affect and then use contrast/lighten or adjustment layers of contrast, curves and levels to try to lighten that area up a bit. for me, i'd just crop that really dark area out on the right.
and yes, i'm talking
psp 7.xx here. what version are you using?
K.