Try NifSkope
Rightclick on the NiTriShape you want to remove collision from, then Block->Insert->NiStringExtraData. In Blocklist type in at Value of NiStringExtraData "NCO". Then click on the NiTrishape, see in Block Details and where it reads Extra Data type in the number of the NiTrishape, so that NiStringExtraData gets linked to it, done!!! [img]http://niftools.sourceforge.net/forum/images/smilies/icon_wink.gif[/img]
EDIT: Go to "Render" and activate "show hidden". Some meshes have additional collision boxes. If it has it will now show up as grey shape, which will have to be removed by rightclick on it->Block-> Remove!!!
http://niftools.sourceforge.net/forum/viewtopic.php?f=17&t=2577