>Application code assumes current directory is user directory, it creates user specific files.
>It is huge work to find all places and change them all.
>
>I tried
>
>LOCAL vcurdir
>vcurdir = sys(5)+curdir()
>SET DEFAULT TO ..\exedirectory
>FOXYPREVIEWER()
>set defa to (m.vcurdir)
>
>but libhpdf.dll is still copied to every user directory.
>Only foxypreviewer_settings is stored in exedirectory in this case.

How about:

LOCAL vcurdir
vcurdir = sys(5)+curdir()
lcPath = SET("PATH")
SET DEFAULT TO (JUSTPATH(SYS(16,1)))
SET PATH    TO

FOXYPREVIEWER()

SET PATH TO (lcPath)
set defa to (m.vcurdir)