I burned a movie on a +R DVD. It plays on my computer but not my Mintek DVD payer. Why is that?

Do you use a DVD burning program or DVD copy program to convert ISO file to DVD? Normally, if you not, it is just data DVD and not a playable DVD disc for DVD player machine.
You can try to use some programs to copy ISO to DVD such as Leawo Blu-ray Copy or Windows Disc Image Burner. Microsoft has included a default feature of burning ISO files to DVD disc.

I recomend that you clean the lens to see if that makes a difference.
Also you might want to look at my Tip on dealing with DVD's that jump.

If it is a commerical disc then your laser may be going out...if it is a material that was burned on a blank disc it might be formatted incorrectly for your player.

I would get an optical laser lense cleaner ( it is basically a cd that has fine soft brushes on the underside to clean the laser lense )

something like :

laser lense cleaner link

If your DVD player is less then a year old, still under manufacturers warranty. I would suggest to call the manufacturers to get the name of an authorized dealer near you to fix it.

The part that reads the DVDs is defective. I would suggest to try cleaning it using a lens cleaner, hopefully that works.
If the cleaning does not work, it might just be cheaper to buy a new one instead of repairing this one.

Check the file format.

When you burn dvd's to play on DVD players dont burn them as Data dvd they will not play. When you burn the DVD movie try to burn it using a DVD player compatible profile and this depends on the application software you are using to burn the DVD.

Do the DVD play on your computer from DVD or even from the file on hard drive.

If it does not play from the file on hard drive then the file is corrupted on downloading or you dont have a proper dvd palying software like PowerDVD

If it plays from the software but does not play from the DVD on your computer, then it means your DVD burner softaware corrupts file information on burning. Try using a different burning software.

If it plays DVD on your computer but not on the DVD player then your DVD burning profile you selecting is not compatible with your player its possibly burning Data DVD.

What other regions are you trying to play besides US/CAN?