AoEd/RoRd are two modified versions of Ykkrosh's GeniEd(1) that can open *.dat files of the game.
More information and official discussion/tutorial topics can be found below:
Z13.invisionfree.com
Aoe.heavengames.com
Known Issue:
Everytime you change to other program or windows when running AoEd/RoRd, a message "use of uninitialized value in numeric eq <==> at PERL2EXE_STORAGE/UI.pm line x" would appear. This problem had been existing even since the original version of GeniEd and can not be fixed. To avoid this issue, try not to tab to another program or window when running AoEd/RoRd.