Physical description:
A blue looking robot with brown hair
Dabs of yellow and red a bit
Hikari's navi symbol (red circle with a black line going through it)
Personality:
This person (Netnavi) is a very helpful netnavi.
But this changed sometimes throughout the story of few games. In example of the 3rd game, Megaman.exe 'accidentally' helps Mr. Match (A WWW World Three Netmafia operator) set the SciLab and the Net on fire, causing Lan and Megaman to get really stupid.
Their general demeanor is to be a helpful netnavi and bust viruses but yet again this changes.
During the Den Battle/City Battle tournament in Megaman Battle Network 4 Red Sun/Blue Moon, during the preliminaries, megaman has to fetch an important data from 'Mettaur Village' to progress.
There is an evil navi who gives Megaman the data.
The following dialogue goes:
*after obtaining data*
Evil Navi: Hey buddy, wanna go delete those Mettaur?
Mega man: No! Why should we do that?
Evil Navi: What the? We're SUPPOSED to delete viruses! It's our JOB, pal.
Megaman: You're right, but what you're doing is plain bullying!
Evil Navi: Alright punk you're going down with them!
(I don't know the exact dialogue this was the best i could get to.)
Equipment and Abilites:
Megaman.Exe has a wide variety of Battlechips, or equipment, he can use.
The much basic battlechip is a cannon, which allows megaman to charge a cannon in his right arm, causing a bit of damage to opponents.
He can also 'merge' chips to apparently cause a phenomenon known as 'Program Advance'
Which allows him to use a much larger attack.
There are way too many battlechips to show so i'll skip them...
Another ability he has is that he can 'Style Change' or 'Double Soul.'
Yet again this is more complex but in short:
Style change can occur how you fight in-game (and in the anime as well. Video games 2-3 only)
For example, if you use chips a lot that are based on attack, you get a Custom style.
There are 4 elements:
Wood
Elec
Aqua
Fire
You can get an element of one of these styles.
Here's a weakness chart
Wood>Elec>Aqua>Fire>Wood
Double Soul is like style change but is more complex (Games 4-5 only but i don't know if six has it).
In the game you have to sacrifice a certain element chip.
You get a certain element blah blah blah your power changes etc.
Historical Background:
As a child, before he became a netnavi, Megaman.exe was Hub Hikari, Lan's 'dead' brother.
At a young age, Hub died with a heart disease known as HBD or HemogloBin D.
Lan's father decided that Lan would probably need a brother, and thus Megaman.exe was born as a 'reincarnation of Hub' to Lan.
(Hub IS Megaman.exe. See the final boss intro of MMBN5.)
They got to where they are today as crossing the world in search of deadly viruses that could destroy their planet.