Welcome to the CD Freaks forum
I have had fairly poor experience of using Windows Media player for playing back DVDs recorded in a standalone DVD recorder (a few Lite-On's in my case). In a few cases, Windows media player would refuse to play the disc claiming there is a licensing issue with the DVD. In some other cases, the video would not display properly, drop frames, etc.
If you have any other playback software on your PC, such as PowerDVD, WinDVD, Nero Showtime, etc. I would recommend giving one of these a try to see if any will play your recorded DVDs properly. When Windows media player plays back a DVD, it actually relies on an MPEG2 codec from one of the installed players in order to play the disc. If you really need to use Windows Media Player for playing back DVDs, the only 3rd party software codec that seems to give the least issue for me with Windows Media Player (at least with discs recorded in a Lite-On) is WinDVD.