A friend burned a video on a DVD-R today for me. It works on my computer, but if I play it on my DVD player, the video is distorted, like a scrambled cable channel. 
If I ask him to burn it again, what I can I have do to prevent this from happening again?
Heres a crazy idea, go out and buy it!
Assuming it’s not actually an unauthorised copy of a copyrighted work… it may be that the video was compressed using too low a compression ratio for your player (too high compression degrades the quality, but too low compression results in high-bandwidth video that may be too much for the buffers in your player)
So, basically, I need a better DVD player.
As for unauthorized copies, one of them is of DVD reviews he did on YouTube that has clips. I wonder if that will work or it will be clear, distorted, clear.
Well, that, or a lower quality DVD recording. Professional DVDs tend to use 4-5 Mbps, to avoid the very compatibility problems you are finding.
The only time I’ve seen scrambled output is when I try to PAL DVD on a NTSC DVD Player. My Philips DVD player can play both, but that is unusual. Windows doesn’t care since neither format is ‘native’ to it.
When you play the disc in Media player check the properties. A NTSC disk will be XXXx480. XXX will usually be 640 or 853. PAL is usually XXXx540 as I recall. PAL disks are also 25fps instead of 30fps.
Yeah, not being within the DVD spec would be my guess.