DVD is the only format that judders?
VLC does not use the directshow DVD decoders so it wouldent be affected by a directshow codec problem problem. And if this is a codec problem you almost NEVER need to format to fix it.
Well one of the first things I would do sence you said first it started with a few DVDS and then gradualy started to happen on all DVDs is to use a cleaning kit on your drives. Not all DVDs are the same quality (even retail) and diffrent discs can be vaulnrable to dirt levels that others are not.
While PowerDVD is a direct show based player it does not use it's own codecs to play DVDs (the .ax files zoom player uses) but rather it has a version of the codec embeded into the powerDVD main exe file. The external codecs are only there for use of 3rd pary apps like Windows Media Player or Zoom Player (or any other directshow based player that can play DVD). The player should not be vulnrable to codec conflicts. WinDVD definitly works like this and I am almost shure PowerDVD does as well.
Sence you said you are using Zoom Player Pro you can use it's custom playback mode to force it to use ONLY the codecs you tell it to use. This can 100% eliminate the possability of a codec problem as it will only use the decoders you tell it to use. If you are using custom playback mode and it still has problems and there is nothing wrong with the .ax file versions of the codecs you can be pretty sure the problem is somere other then yur codecs.
You may want to find out what the file name for the PowerDVD audio and video codecs are (you can get zoom player to tell you the names) and then search your machine for these files and see if there is any duplicates and if any of them are diffrent file sizes. If they are then delete them and re install PowerDVD (sometimes removing powerDVD wont delete all the codecs and if one is damaged it could still be on your machine). Still I doubt it is a codec problem.
If you realy want to try to be 100% sure it is not a codec problem then there is the "last resort" option. This is a process that involves using Zoom Player to totaly un regester every single directshow component on your machine and then run a .bat file to re-regester the defualt codecs that are installed on a fresh OS install. It is a perfictly safe procedure and I have used it many times myself. It can be fond here.
http://www.inmatrix.com/articles/mediasetup3.shtml
If none of this helps then the problem is proly with DirectX or your video drivers. but it would be very strange for only DVD to mess up and nothing else if this is the problem.
Oh yea... If you have one try and play an SVCD as it will also use the same codecs as DVD will. See if they judder as well.
Well hope some of this helps.
