|"DVDs don't have data on both sides."|
I have several double-sided DVDs in my collection. Most of them store the 16:9 version of a movie on Side A, and the 4:3 on Side B. I also have a few DVD-Audio "hybrid" discs: high-res 24/96 DVD-A on one side and standard DVD-Video on the other.
WMP will not play DVD-A, if that's what your side B contains. Take a look at the DVD in WIndows Explorer. Does the Audio_TS folder contain ATS & AOB files?
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