when you drag a shader down to place in the library, example place would be "My Shaders"

the files can then be found (default, not sure if changable, probably is) in
C:Documents and SettingsMy DocumentsEoviaCarrara 5My PresetsMy Shaders

above location is dependent on many things, windows xp screenname, unless one wasnt
set and all users use the same, it would be in "All Users", prefered location, i'm sure is an
option in C5 that can be changed, and this is assuming you run winxp too :) other OS be dif

another way to find, would be remember the name of the shader when you save it
say you name it "My first shader", then just use the search for files option, and search for
the file "My first shader.cbr" which you can just copy/paste to a new location if you want
or leave it, and just view the path to the file for future refferences