Thanks for your input marc, all the pc's are all the same, i forgot to mention that we use canopus storm capture cards complete with front bays. The students capture anologue via video players and dv using sony dvcams (dsr11) The removeable HDD system we use is just a 3.5" bays and caddies, the HDD normally range from 50gb to 120gb, all at 7200rpm. These are set as slaves. The majority of are students tend to stick all their work straight to the root of the drive, rather than organise in folders, which we do recommend they do but they never seem to listen. I must admit the common factor in all the projects that go wrong, is that there has been no file management. We do limit the students access to the pc, they cannot install any software, codecs etc. The most common problem we have is to do with the avi files, the video disappears but audio is still there, the video from one clip seems to assimulate another clip , yet leaving the audio original. The bizzare thing is that checking many forums, no one seems to have these problems, they have many other types but never the same as our, which make me think that it is something to do with the setup. Any help offered would be appreciated.