dvr drive problems? or dvd_r dvd+r problems?

Well i have the new sony dual layer drive to burn dvd . I convert my avi/mpeg movies using dvd santa win avi and some other programs i have to format to dvd . But when i burn them on my dvd-r / dvd+r it plays on my dvd player for like 20-40 minutes and the movies starts freezing and sometimes cuts off. I have tried sony dvd-r/dvd+R and platnium brand dvd-r/dvd+r . and they still cut off with both of the types of
dvd r i use / brands . so im wondering is maybe both of the brands of dvd r suck or is it my sony dvd burning rom .
Hopefully some one understands what im saying .

I have some videos in a dvd-r, but I can’t watch this in my computer, it has windows xp,and this asks for a decodifer, How I can watch this?, in my dvd plauer (toshiba), it didn’t run nether. i hope somebody can helpme..tank you.

I copied vcr tapes to a dvd /r but it wont play on computer,dvd player only on the copy machine