點解部腦讀唔到隻dvd?

There are 2 reasons:-
1. Your computer is not able to read DVD Disc
2. Your reader was broken down.

You can check is the computer fitted with a DVD reader by check the reader's disc entrance, if you can't see any thing written as DVD, means your reader is not a DVD Disc reader, maybe it's only a VCD Reader or a compact disc reader.