OK. I asked because older versions didn't support Adobe RGB jpegs by default.
Is your computer screen colour calibrated?
Did you know that the LCD on the D200 doesn't display Adobe RGB images correctly, so you can't trust it?
Did you know that if you have some of the picture enhancement options set as per the factory default it causes the D200 to revert to sRGB anyway?
I would have a read of Thom Hogan's guide on this subject. The sRGB space is quite limited.
Many/most web browsers can't display the Adobe RGB colour space! Firefox can, but you have to enable it. To convert from one to the other, you need to use the save to web option in Photoshop. I use the adobe option (when I rarely don't shoot in RAW), but have changed the settings per Thom's suggestion. They look much better then.
I have them at Sharpening +2 (Thom suggests +1) Tone Normal (0), NOT Auto Color Mode 1 or 2 (for 2 you must use Adobe RGB) Saturation Normal (0). Going up from that looks really vivid, great on cloudy days! Hue is up to you. I leave mine at 0.