But why do the pictures on the LCD look very very bright while on the PC they are very dark and muddy.
It can all be fixed with a little curves in ps7.0 but it puzzles me.
I'm not sure why Canon chose to boost the brightness so much on the LCD; perhaps so it could be seen easier in bright sunlight - but unlike a conventional digicam, the appearance on the LCD has nothing in common with the actual exposure.
This is true of every 10D I've seen or used. There is a menu adjustment where you can drop the brightness, but whether or not you want to do this depends on how you use your camera and whether you have an Xtend-a-View (recommended) for viewing the LCD in bright sunlight. The Xtend-a-View is a simple 2x loupe/sunshade which you can put around your neck on a lanyard cord (I use them with all my cameras). So you can adjust the brightness of the LCD way down to somewhat correlate with the image capture itself and use the Xtend-a-View or - and this is ALWAYS the better way to go - use the histogram to quickly check your exposure and correct if necessary. You may need to tinker with the exposure compensation to get it just the way you want, but overall it will be a gigantic step forward as you have undoubtedly already discovered.