A question came up the other day on the Symantec Partner distribution list which is well worth discussing here. The question related to what happens with regards to indexing the list of files INSIDE an ISO file. Some people might already know that if you archive a ZIP file then the contents of the zip are indexed. But that's not the case for an ISO file - I tested it.
There is actually an article which describes which files are and which file aren't indexed:
Most of the files on the list make sense, because they aren't 'clear' files:
.ABS.AIF.AIFC.AIFF.ASF.ASX.AU.AVI.BIN.BMP.BP.C2D.CBT.CCD.CD.CDI.CHM.CIF.CUR.DAT.DAO.DVS
.DWI.ENC.EVT.FCD.FDM.FP.GCD.GI.GIF.GTS.HLP.ICO.IMG.ISO.JFI.JFIF.JIF.JPE.JPEG.JPG.JTF
.M1V.M2V.M3U.MDF.MDS.MID.MMM.MOD.MODV.MOO.MOOV.MOV.MP2.MPA.MPE.MPEG.MPEGA.MPEGV.MPG
.MPM.MPP.MPV.MSO.NRG.OLE.PAB.PDI.PJPEG.PLS.PNG.POI.PST.PUB.PXI.QT.QTM.QTW.RA.RAM.RAW
.RM.RMI.RMJ.RMX.RP.RV.SND.SNP.SWA.SWF.TAO.TIF.TIFF.VDO.VIV.WAV.WMA.WMV.Z01.Z02.Z03.Z04.Z05
.Z06.Z07.Z09.Z10.Z08.
But .PLS, .CHM, .ISO are a bit surprising. The technote also explains how you go about extending the list - have you ever done that? I know I've not.