Rejoining VOB files tends to cause glitches -- mostly because the VOB files were not ripped correctly. Ideally, you want to access the video data from within the structure, meaning "IFO mode" on something like
DVD Decrypter or VOB2MPG Pro.
I've had mixed results with Womble MPEG Video Wizard, so I don't suggest it.
Womble MPEG-VCR is not suggested for this task.
VideoReDo claims to work on this, but I had mixed success with it, too, in earlier versions (pre-2010) and doubt it's changed much.
TMPGEnc MPEG editor probably won't fair much better.
The "MPEG editor" programs really aren't designed for merging VOB files.
Oddly enough, TMPGEnc DVD Author (or the upgrade version TMPGEnc Authoring Works) can sometimes merge VOB files, because it also accesses the video via the structure using the IFO. "Import DVD" or some such command that I forget off-hand because I never use it.
WMP is never a good choice for video playback of any kind. For DVDs, use PowerDVD or WinDVD -- both have always been the preferred choice. For various video files, use a codec-less player like VLC or GOM. VLC can also play DVDs pretty decently, if you don't want to buy the better DVD players (as WinDVD and PowerDVD are both payware, although there are some trials to give test drive with).
If you have trouble with VOB2MPG, know that the author is a really nice guy, and he'll always reply to troubleshooting and error reports.