You roughly know what it is and when it was made.
The same frame was used on various models over the years, the color of the frame usually gives you a good idea on when it was made and what model it is.
If you can't find a 1999/2000 XCR or a early 2000's i-Drive that's painted black then the bike has either been repainted or it could be a promotional bike that was made for some other company.
The only difference between the different versions of the XCR/i-Drive bike models is the color of the frame and the quality or brands of the parts that's supplied with the new bike.
If the bike has been repainted or parts have been changed then it isn't an accurate version of a certain model.
Parts on bikes such as derailleurs, fork, shock, shifters, crankset, seat, handlebars, etc, etc, can all be easily changed and they aren't an accurate way to ID a bike.
You could contact GT and ask if they cold ID the bike through it's serial number but they probably won't be of any help.
Find a XCR or i-Drive on the following link with similar parts and just call your bike that model.
http://www.bikepedia.com/QuickBike/Bikes.aspx?
My advice is to stop worrying about what you have and to just ride it.