Like several others here, I have both v3 & v4 installed in different folders.
I've just noticed , though, that some of the common settings are shared _ I was trying to configure v3 to have pathplayer disabled and v4 to have it always enabled, but changing it it one version actually changes it for both versions.

I don't know what other parameters are shared by both versions & which can be set independently - I guess it depends on how/where the settings are saved ?

I've also noticed that I need to wait a few seconds between shutting down v3 & launching v4 otherwise v4 crashes at launch.

Hi cybmole. I have noticed some unusual things too with Common Settings (with both installed). I uninstalled (using Add/Remove pgms) the v3. Found that I wasn't using it anymore anyway and can always add it back.

so was fengtao correct - i.e. did uninstalling v3 leave your v4 & your patin couffin drivers intact ?

If you & fengtao both say it's safe that will be good enough for me

I had some problems but I think they were related to some corrupt user data in XP that happened about the same time--had to create a new user and move all the files over from the old one. I think some of the stuff didn't make the transfer. I had to redo my registration and manually move the profiles for DVD to Mobile (which I have heavily customized). One thing for sure I have learned here is to always trust what Fengtao says about DVDFab.