As long as the nfo file conforms to the XBMC nfo standard then it will be used and not overwritten.
By XBMC nfo standard I mean :-
<movie>
<title>Jumper</title>
<rating>5.9</rating>
<year>2008</year>
<top250>0</top250>
<votes>37,708 votes</votes>
<outline>A genetic anomaly allows a young man to teleport himself anywhere. He discovers this gift has existed for centuries and finds himself in a war that has been raging for thousands of years between "Jumpers" and those who have sworn to kill them.</outline>
<plot>David Rice is a high school student in Ann Arbor, abandoned by his mother at five, enamored with Millie, a fellow student, and picked on by at least one classmate. On a winter's day, while about to drown, he discovers he can transport himself instantaneously to anyplace on earth. He leaves town, goes to New York City, robs a bank vault, and comes to the attention of a shadowy group of government hunters. Eight years later, the hunters, led by the murderous Roland, get a fix on David. He heads home, searches out Millie, invites her to travel with him, and only later realizes that Roland and his crew are seriously deadly. Is everyone close to David in danger?</plot>
<tagline>anywhere is possible.</tagline>
<runtime>88 min</runtime>
<thumb></thumb>
<mpaa>Rated PG-13 for sequences of intense action violence, some language and brief sexuality.</mpaa>
<watched></watched>
<id>tt0489099</id>
<genre>Action / Adventure / Sci-Fi / Thriller</genre>
<credits>David S. Goyer / Jim Uhls</credits>
<director>Doug Liman</director>
<premiered></premiered>
<studio>Twentieth Century-Fox Film Corporation</studio>
<trailer>
www.totaleclips.com/Player/Bounce.aspx?eclipid=e35335&bitrateid=314&vendorid=102&type=.flv</trailer> <actor>
<name>Hayden Christensen</name>
<role>David Rice</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMjExODA5MjYyOF5BMl5BanBnXkFtZTcwNzA2NzYyMQ@@._V1._SX100_SY139_.jpg</thumb>
</actor>
<actor>
<name>Jamie Bell</name>
<role>Griffin</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTk4ODY3ODE4Nl5BMl5BanBnXkFtZTcwOTQ3NTgzMQ@@._V1._SX97_SY140_.jpg</thumb>
</actor>
<actor>
<name>Rachel Bilson</name>
<role>Millie Harris</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTU1NjA4OTM5MF5BMl5BanBnXkFtZTcwNzAyODQyMQ@@._V1._SX100_SY136_.jpg</thumb>
</actor>
<actor>
<name>Diane Lane</name>
<role>Mary Rice</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTcwMzY1NDkzOV5BMl5BanBnXkFtZTYwNjE5NDM4._V1._SX100_SY101_.jpg</thumb>
</actor>
<actor>
<name>Samuel L. Jackson</name>
<role>Roland</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTM1NjI5NzI4OV5BMl5BanBnXkFtZTcwOTk0NzYyMQ@@._V1._SX100_SY105_.jpg</thumb>
</actor>
<actor>
<name>Michael Rooker</name>
<role>William Rice</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMjA5NTc5NTQ2MV5BMl5BanBnXkFtZTcwMDUyMDUxMQ@@._V1._SX100_SY122_.jpg</thumb>
</actor>
<actor>
<name>AnnaSophia Robb</name>
<role>Young Millie</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMjE4NjQ3ODI4OV5BMl5BanBnXkFtZTcwNzM1OTUyMQ@@._V1._SX99_SY140_.jpg</thumb>
</actor>
<actor>
<name>Max Thieriot</name>
<role>Young David</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTc0MDE5MDgzOF5BMl5BanBnXkFtZTcwMTg2MDUyMQ@@._V1._SX100_SY135_.jpg</thumb>
</actor>
<actor>
<name>Jesse James</name>
<role>Young Mark</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BODA4MDI0NDE4NF5BMl5BanBnXkFyZXN1bWU@._V1._SX93_SY140_.jpg</thumb>
</actor>
<actor>
<name>Tom Hulce</name>
<role>Mr. Bowker</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTc5MzU5NjQ2OV5BMl5BanBnXkFtZTcwMTc3NTgxMQ@@._V1._SX100_SY140_.jpg</thumb>
</actor>
<actor>
<name>Kristen Stewart</name>
<role>Sophie</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTQyODMxOTE0Ml5BMl5BanBnXkFtZTcwNTA2NjIzMQ@@._V1._SX100_SY132_.jpg</thumb>
</actor>
<actor>
<name>Teddy Dunn</name>
<role>Mark Kobold</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMTc4Mzg1NjcwOF5BMl5BanBnXkFtZTcwOTg5MTA2MQ@@._V1._SX100_SY125_.jpg</thumb>
</actor>
<actor>
<name>Barbara Garrick</name>
<role>Ellen</role>
<thumb>http://ia.media-imdb.com/images/M/MV5BMjE1MjI1OTY5OV5BMl5BanBnXkFtZTYwMDc3MTU4._V1._SX100_SY66_.jpg</thumb>
</actor>
<actor>
<name>Michael Winther</name>
<role>Day Bank Manager</role>
<thumb></thumb>
</actor>
<actor>
<name>Massimiliano Pazzaglia</name>
<role>Italian Desk Cop</role>
<thumb></thumb>
</actor>
</movie>
nfo files that do not use this standard will be overwritten (for example scene nfos files).
It would be possible to rename these files, I am not sure it is neccesary though.
Did you know that media companion uses medianfo.dll to display all file information as follows :-
General
Filename :- E:\Movies\Jumper.avi
FileSize :- 998 MiB
Format :- AVI
Format Info :- Audio Video Interleave
Video
Duration :- 1h 28mn
Resolution :- 704x304
Codec :- XviD 1.1.2
Codec Link :-
http://mediaarea.net/XVIDFramerate :- 23.976 fps
Video Bitrate :- 1 123 Kbps
Profile :- Streaming Video@L1
Scan Type :- Progressive
Audio
Audio Codec :- AC3
Codec Link :-
Channels :- 6
Mode :- Constant
Bitrate :- 448 Kbps
Min Bitrate :-
Sample Rate :- 48.0 KHz
Just click the "File Details" Button located on the main movie browser page.