Has the copy protection been removed from aforementioned DVD/BD ISOs? If not, you're going to need an app like AnyDVD HD, DVDFab or MakeMKV to decrypt and remove the copy protection on-the-fly before Media Center can play them. PowerDVD does support playback of encrypted (copy protected) discs and ISOs, but Media Center does not and can't play encrypted discs and ISOs unless the copy protection has been removed using one of those apps.
For SACD ISOs, those are different and you shouldn't mount those nor do you have to worry about any copy protection. Just directly import the SACD ISO into Media Center and if your DAC is DSD capable, enable DSD bitstreaming and it should play fine. If you don't have a DSD capable DAC, Media Center will convert DSD to PCM on-the-fly and play that (be warned, DSD to PCM conversions can be very resource intensive and it's recommended to have a somewhat decent PC or Mac in order to do this on-the-fly without hiccups). An alternative to importing the SACD ISOs is to use an app like sacd_extract and extract DSF files from a SACD ISO and use/play those instead.
