^^WHAT?!? Not 'powerful' enough?? What do you mean, that it requires some health drink or something?? (Sorry, No offence meant)
@super jango: There could be several reasons for that:-
1>The movie files in the DVD may be corrupt.
2>The DVD might be scratched.
3>The DVD might not have been burnt properly.
4> Your drive might be faulty. (Is it old?)
5>You might not have the codecs required.
Does reading data from normal discs take a long time for you? In that case, it might be the DVD Drive which is faulty.
Check the DVD on some other PC. Also, check if other DVDs or CDs work on your PC (Data discs). Also, ensure that you have the required codecs to play the file (most likely you do). If you find the DVD drive at fault, go get a drive cleaning disc, and try to save it. If it still doesn't work, get the drive replaced (If it is in warranty period, try to get it repaired).
Its not your PC... unless you've got codec problems in which case, you just have to install some codec pack (I'll prescribe K-Lite Mega codec pack, its always on digit DVDs).