The best way I can explain it to myself is as I described in post 22 above. Whether this is technically right I don't know. There is masses about this problem on the web, and the solution given is always to install approprate drivers on the initial installation via the F6 option or to set the SATA operation to IDE in the BIOS. On the machine I am writing this on the BIOS setting is obvious. On the Viglen I am trying to install on there just doesn't seem to be the option in the BIOS - yet surely there must be if I can find it. I am experimenting at the moment.