In Scott Kelby's, The Photoshop Book for Digital Photographers, the author recommends changing Photoshop's default settings to Adobe RGB (1998); however, the last time I calibrated my monitor, a LaCie 22blue, those settings became the default, so should I replace them with the Adobe settings? I calibrated this monitor not with any external device, but through the system preferences of my Mac running Tiger, and those setting replaced the "bad" Photoshop settings the author makes mention. Thanks for help!

Monitor calibration has nothing to do with your working colorspace. Calibrate your monitor, load those settings at system start (using Colorsync, Adobe Gamma or your own calibration software) and load your working colorspace (in this case AdobeRGB) via Photoshop color management preferences.

Thanks for your reply, and please forgive the delay. Well, I'm a little puzzled by your response because when I calibrate my monitor, does that not affect the colors I see, and would I not want the color space on my monitor to approximate as closely as possible the color space of all other devices?

What was really behind my original question was simply that when I went to change the RGB color space in Photoshop, I expected to find the default color space RGBIEC61966-2.1 -- but instead I found the profile of my monitor calibration listed and wondered why and if or when should I use that profile and what sort of implications that profile has for monitor calibration--questions which perhaps I should take up with LaCie.

All the profiles for your system get dumped into the same directory, so there's monitor profiles, printer profiles, maybe even camera and scanner profiles. But those are all device profiles, which is not what Photoshop is asking for in the CM dialog (even though they show up as options).