yes I concluded that the disc would be allright. I accept the point that that is no safe assumption. But in the meantime I tried Live CDs of other recent distributions : Mint, Dream the same there...

Right now I suspect that there might be a problem with the graphic card. After I push Ctrl Alt Del the screen is works again and the system is going through its normal shutting down procedure.

I have been using Linux only occasionally in the past and would like to switch to Linux now when I manage... Its hard to troubleshoot when you do not know the operating system and you need to have the system working in a limited time span.