bonplay

I have a problem that perhaps someone here can help me with. I have used DVDD in the past with DVDShrink, and from time to time I have burned DVD-R's that will play fine on a tabletop dvd player, but will not play on my PC. Windows Explorer will not "see" the disc. I use Power DVD with a Pioneer DVR-106D drive. I've upgraded to XP Service Pack 2, and still I am not able to play these discs on my PC. Does anyone have any sugestions? Thanks in advance