Since I am new to VLC (which is a wonderful media player!) I spend a lot of time sorting out the following problem: I was running Firefox 2.0.0.1 on Win XP SP2 and installed VLC 0.8.6a. After installation I was unable to run VLC embedded in Firefox, although I had marked the "Install Firefox plugin" checkbox.
In the VLC Play How To (play-hoto-en.pdf) on p. 47 is mentioned a possible solution: “Quit Firefox or Mozilla. Copy the two files in VLC_Installation_folder\mozilla (usually C:\Program Files\VideoLAN\VLC\mozilla) to your mozilla plugins directory (Usually C:\Program Files\Mozilla\plugins or C:\Program Files\Mozilla Firefox\plugins). Restart Firefox or Mozilla.”
I was, however, unable to find both of these files (npvlc.dll and vlcintf.xpt); only npvlc.dll was available.
Now I downloaded VLC ver 0.8.5, and everything went as expected, including the installation of both files in the Mozilla Firefox\plugins directory.
Subsequently I examined the zip-version of VLC ver 0.8.6a installer and found no trace of vclintf.xpt. I suppose it somehow has been forgotten to include it!
Hope this helps someone and may save some time!
Jorn