There are various different versions of some of these texture sets which can be difficult to track down. Make sure you read those install instructions carefully & get the correct ones. If in doubt get them all. Most of them are posted in the SimV Essential Files sections. http://www.simviation.com/fs2002utilities_ess1.htm There might be others posted in the Scenery design section. You need the standard texture sets, not the design programs themselves.

I suggest you get Gerrish Gray's latest tree library (Gerrish's Trees Library for FS2000/2 Release 3) while you're about it. This is very popular & commonly used by scenery designers.

Hope this is some help.