Infinity Explorer is just a browser - viewing various egine files.
To edit, you have several options:
1. Use Shadow Keeper
This will allow you to edit your save games - but not the basic nature of the game itself. Useful for modifying NPCs, your character, adding items, levels, stats, etc.
Found here:
http://www.mud-master.com/shadowkeeper/
2. Use Infinity Engine Editor Pro - a graphical interface modding utility. You can make major game modifications with IEEP.
Find the IEEP at:
http://www.teambg.com
3. Use Near Infinity - A little less user friendly, probably, but very powerful.
Found here:
http://www.idi.ntnu.no/~joh/ni/
4. WeIDu - the most effective modding tool, and also the most complex. You must learn a simple programming language to create dialogue and scripting files and the like, but the beauty of this program is that mods properly made with it are completely compatible.
Found here:
http://www.cs.berkeley.edu/~weimer/bgate/