"J David Ellis" wrote in message
...
When XP SP2 Display Properties Settings shows Color quality as "Highest
(32 bit)", what does that mean in terms of number of bits per RGB channel?

This means each channel gets 8 bits. The extra 8 bits are either wasted or
used for an alpha channel (transparency).

Here's how Wikipedia describes it:
http://en.wikipedia.org/wiki/Color_depth#32-bit_color