trouble shooting linux

hello this is laya. I need some help regarding linx installation and also trouble shooting.
i installed linux mandriva 2009 in my school months ago and now it says password expired and doesnt start up. So i was wondering if there could be any default password for linux versions??? and next is that i am unable to insall linux on a machine which is a dell machine. I am unable to get a mesage which asks press F1 or ... to start boot from CD .Dell machines have F10,F2,del keys to start booting from CD but i am unable to..i have reset the CD/DVD drive options as the 1st prority too.Can i have any solutions to these?

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