Top message: Newbie needs software info. by Katithecutie
Replying to: Re: Newbie needs software info. by kellykell22
MPT (data cable) software download
They have the original v1.23, the v2.16 update, and the newer full version 3.11 (haven't tried 3.11 myself).
I posted a link to this other site a while back, and the download links are still good:
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Shop for accessories specifically compatible with the Motorola V400.