After downloading a movie and burning it to a DVD I can't get the DVD to play on a stand alone player although it plays thru my PC. I have tried differnt brands of players and different media brands e.g. Ridata, kypermedia. I"v also tried slowing the burning speed to 2x.

Any ideas would be appreciated.

1st!!! check the specifications to your set-top player to check it can play dvd-r's. See if it specifies brands (some do.)
Which program are you using to convert & burn the video? I could suggest TMPG but other than that to see both http://www.videohelp.com/ & http://forum.dvd-guides.com/ & perhaps http://www.videohelp.com/tools

All the DVD players play +R and -R. My Dell came with the Sonic Record Now Program .