After the computer reboots, at start up there'd be an error submitting process and after that an IE window comes up from Microsoft and tells me it was "DVD For Free (DVD43.SYS)" that caused the problem.
See I don't even have "DVD For Free". However, I do have DVD CSS+Region Free installed on my computer.
How do I avoid the problem from happening again? As I said it doesn't happen often but just now I put the same CD into the CD Rom and it happened twice in a row. Would be quite gutted if I were doing something important at the same time.