o.k

I'm trying to install mandrake 9.0 and after I've choson the pakages, it start installing. when the install finishes I get this error and it sends me back to the pakages selection

An Error ocurred
some important pakages didn't get installed properly
Either your cdrom drive or cdrom is defective.
Check the cdrom on an installed computer using
"rpm-qpl Mandrake/RPMS/*.rpm"


I know that the cd is a burned copy but I witness it install on other computers. And my cdrom drive never gave me problems


I'm installing it in my class, my teacher and classmates have no idea why this is happenning. please help me