I downloaded a movie step by step part 1 part 2 ect... and when i try and play it on divx it says ''unsupported format this video is in an unsupported format and cannot be played without installing additional DirectShow filters''

have you tred upgrading the software it uses

Try PowerDVD. They support an incredible number of formats and there is a free trial. Also, DVDFAB has a free media player that also supports multiple formats and the download is free. dvdfab.cn- do not be afraid if your browser says there is no cerifificate. I am on that site almost every day.

It can't read the files on the USB, wrong format.

If it's hacked you can play movie discs, if not just if the movie is in DivX, Avi, MPG or MOV format and you play them from a SD card.

If your are talking about a xbox 360 console and you can't play a movie, sometimes its because the movie isn't in one of the supported video formats or is copyright protected. Here are some of the movie formats the 360 will support:
.m4v .mp4v .mov .avi (newer .avi files) .DivX .wmv
You may want to get movies in these formats, or get a converter to convert the format into one of these that will play on your 360, hope this helps!
-Ryan

Some of movies encoded in Xivd (not divX, thought thye are compatible) are not supported my some manufacturers.

One of the following should help
- Re-encode the movies in DIVX format and play them
- Upgrade your TVs firmware to support the latest video formats

you should download a divx player software to play divx files

you device should support these video formats. MPEG4, WMV, H.264 and DivX.
anything else won;t play