dear!DivX is video compression technology similar to mpg ("mpeg" not miles per gal) that requires a codec (piece of software that understands the format) to view. I would say it is safe to download from a trusted site.
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One easy solution is to dowload the AVS Video player "Support for a very wide variety of video formats: apart from regular DVD (PAL, NTSC, VCD, SVCD) formats, also supported are: the entire range of MPEG4 (including DivX, XviD, etc.), MPEG1, MPEG2, AVI, Real Media video, Quick Time files, WMV files (including WMV-HD), H.263, H.264, mobile video formats (3GP, 3GP2, MP4).
This strong compatibility makes AVS DVD Player a universal player" You can dowload it free