You can download DivX5.1.1
here. You need not install the player which is included in this "bundle"; you can simply deselect it.
For DivX5.1.1 codec, please check its settings on Tab "Quality". These can be reached directly through [Start] "Programs"/"DivX"/"DivX codec"/"Decoder configuration Utility". If "Support Generic Mpeg-4" is checked (selected) it will also play XViD encoded movies. If you leave this box unchecked, same movies require a separate XViD's codec (which XViD codec will - provided you've got an XViD-movie loaded - be shown in BSPlayer under "Options"/"Filters", where you also can set its properties).
After its installed you can find the codec "divxdec.ax" in your Windows system or system32 folder. (You can - of course - always use Window's Search).
For other codecs I refer to
adicoto's post (i.e.
this one) where you can find the respective links.