Yes, the games are made XP compatible out of the box (the originals can be made XP compatible very easily). The graphics are just as they were in the originals and it makes no claims otherwise; surely if they had updated the graphics it would be plastered all over the literature and on the box itself!?
A fan patch has been made to increase the resolution of C&C1, the links are in the common problems thread:
Common Problems with TFD (Updated 08/10/2007)