ps3-how do i play realplayer and quicktime files

When i stream from PC to ps3 WMVs work fine, however cant get realplayer files to play (it says "the folder could not be accessed. This content may have been deleted from the media server".
Also quicktime files have audio and no picture , but then it is the same on my PC and i use VLC player.
Dont know where i would download a codec pack, certainly nervous about this in case they contain a virus,
any guidance would be appreciated
thanks