Today Steve commented courteously on the subject at hand

What is your definitions of "accurate"? Lab-correct
wavelengths of the 16.7 million colors possible, how your
camera, multiple apps, your PC's video card and monitor
settings? Yes, they will /always/ be different, and they will
vary according to subject, lighting, brightness/contrast,
photometric settings in the camera, exposure variations, not
to mention lighting brightness and color temperature in the
room(s) or outside as you view these. And, are you using any
color calibration profiles anywhere in your workflow? e.g., a
color profile in PS7 but not Irfanview? And, if you stray into
the tall weeds of printing, all bets are off again, as what is
"accurate" and "right" now is complicated by the concept of
reflected vs. transmitted light.

In the final analysis, though, what is "accurate" or "right"
is a rather personal thing. I've long thought there are at
least 3 defs: 1) what is technically correct including color
temperature, 2) what looks "right" to you, and, most
important, 3) simply what you prefer. 1) has one and only one
answer, but 2) and 3) are infinite and variable from picture
to picture

So, please help us by telling us more of what you're trying to
do, the subject(s) you shoot, whether daylight or indoors
available light or with flash, how you're camera is set-up,
etc., and whether you view yourself as a creative, artistic,
documentary, or some other kind of photographer. All of those
things, and many more, drastically affect any human's
perception of "accuracy" and "right".

Then, there's "precision", which most folks mistakenly think
is a synonym for "accuracy", but is not.

I don't know about color but brightness & contrast is generally suspect
on most LCDs because the angle of view effects that. Brightness &
contrast are also dependant on camera settings and irrelevant when
shooting raw.. and the LCD & histograms don't show raw, just the
processed jpeg. I suppose cranking down contrast in the camera settings
would be the more realistic way of working even if shooting raw but if
you do raw plus jpeg that spoils the effect of applying 'normal' contrast.

Probably you are shooting in AdobeRGB and Irfanview is only able to
assume sRGB. Irfan is great for quick & dirty browsing though.

I'm assuming the D200 is like earlier Nikons and you are seeing a JPEG
preview in your LCD.  What you see  on the LCD will be the result of
your JPEG settings inside the camera.  What you see on your monitor
(assuming that your camera and monitor are using the same settings,
colorspace and your monitor is calibrated should be the same for JPEGs
only.  Your camera will probably have at least sRGB and Adobe RGB 1998
settings, you'll have to check your monitor for it's settings)  Raw
files will be different on your monitor as no settings have been
applied.  I'm fairly new to digital and spent the past few months
dealing with color issues.  I did end up with a Spyder 2 to calibrate
my monitor and have sorted out the colorspace isssues.  I use Adobe RGB
1998 from camera through software.  The colorspace issue will come up
again when sending things to be printed.

There are good tutorials around the internet.  Try

http://luminous-landscape.com/

and

http://www.earthboundlight.com/

and

http://www.cambridgeincolour.com/tutorials.htm

All three of these websites are essentially chronicles of professional
photographers who've made the transition from film to digital and have
documented that transition with tips and tutorials in well indexed
archives.

Good luck!

First don't worry much about the camera display but calibration will
help.  

But you must calibrate your monitor or you are wasting your time if
you want get the best out of your photos.

Also each application must be able to support your calibrated monitor
profile.

You need to start learning about color management in your digital work
flow.  Get Fraser's book on the subject and start there.

**********************************************************

"A combat photographer should be able to make you see the
color of blood in black and white"

                    David Douglas Duncan
                Speaking on why in Vietnam
             he worked only in black and white
     http://www.hrc.utexas.edu/exhibitions/online/ddd/