Darius,
I've taken a look at the shots again. And I am really believing what you are seeing is an effect called posterization. I think you are may be looking at it and confusing it with noise. (I noticed the speckles on the big vase in the foreground).
This effect might be caused by the colour depth of your viewer. It can also be seen when compressing a jpg file very badly (too much). It shows up as a banding effect or a speckle effect from similar colours but different shades.
You can read up about Posterization here.
Posterization - Wikipedia, the free encyclopedia
Only thing to counter this is to save the jpg file with the least amount of compression. I don't know of a viewer for Win98 that is better than what you are using now, but will look around.
Your camera is possibly giving more data than your computer can handle though.
Cheers!